[PATCH 0/2] am: support --always option to am empty commits

Since that git has supported the --always option for the git-format-patch
command to create a patch with empty commit message, git-am should support
applying and committing with empty patches.

Aleen (2):
  doc: git-format-patch: specify the option --always
  am: support --always option to am empty commits

 Documentation/git-am.txt           |  5 +++++
 Documentation/git-format-patch.txt |  5 +++++
 builtin/am.c                       | 18 ++++++++++++++++--
 t/t4150-am.sh                      | 25 +++++++++++++++++++++++++
 4 files changed, 51 insertions(+), 2 deletions(-)


base-commit: b550198c73edd4cc058832dcf74b41aeec2adba2
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1076%2Faleen42%2Fnext-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1076/aleen42/next-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1076
-- 
gitgitgadget

From: Aleen <redacted>

Signed-off-by: Aleen <redacted>
---
 Documentation/git-format-patch.txt | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
index 113eabc107c..a9f2bf94182 100644
--- a/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt

@@ -30,6 +30,7 @@ SYNOPSIS
 		   [--range-diff=<previous> [--creation-factor=<percent>]]
 		   [--filename-max-length=<n>]
 		   [--progress]
+		   [--always]
 		   [<common diff options>]
 		   [ <since> | <revision range> ]
 

@@ -388,6 +389,10 @@ you can use `--suffix=-patch` to get `0001-description-of-my-change-patch`.
 --progress::
 	Show progress reports on stderr as patches are generated.
 
+--always::
+	Patch commits with detailed commit messages,
+	even if they emit no changes. (see linkgit:git-diff-tree[1])
+
 CONFIGURATION
 -------------
 You can specify extra mail header lines to be added to each message,

-- 
gitgitgadget

From: Aleen <redacted>

Signed-off-by: Aleen <redacted>
---
 Documentation/git-am.txt |  5 +++++
 builtin/am.c             | 18 ++++++++++++++++--
 t/t4150-am.sh            | 25 +++++++++++++++++++++++++
 3 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/Documentation/git-am.txt b/Documentation/git-am.txt
index 0a4a984dfde..de5d11e404c 100644
--- a/Documentation/git-am.txt
+++ b/Documentation/git-am.txt

@@ -16,6 +16,7 @@ SYNOPSIS
 	 [--exclude=<path>] [--include=<path>] [--reject] [-q | --quiet]
 	 [--[no-]scissors] [-S[<keyid>]] [--patch-format=<format>]
 	 [--quoted-cr=<action>]
+	 [--always]
 	 [(<mbox> | <Maildir>)...]
 'git am' (--continue | --skip | --abort | --quit | --show-current-patch[=(diff|raw)])
 

@@ -159,6 +160,10 @@ default.   You can use `--no-utf8` to override this.
 	countermand both `commit.gpgSign` configuration variable, and
 	earlier `--gpg-sign`.
 
+--always::
+	Apply patches of commits with detailed commit messages,
+	even if they emit no changes. (see linkgit:git-format-patch[1])
+
 --continue::
 -r::
 --resolved::

diff --git a/builtin/am.c b/builtin/am.c
index 8677ea2348a..d11efc16f92 100644
--- a/builtin/am.c
+++ b/builtin/am.c

@@ -124,6 +124,8 @@ struct am_state {
 	int ignore_date;
 	int allow_rerere_autoupdate;
 	const char *sign_commit;
+	int always;
+	int empty_commit;
 	int rebasing;
 };
 

@@ -1249,8 +1251,12 @@ static int parse_mail(struct am_state *state, const char *mail)
 	}
 
 	if (is_empty_or_missing_file(am_path(state, "patch"))) {
-		printf_ln(_("Patch is empty."));
-		die_user_resolve(state);
+		if (state->always) {
+			state->empty_commit = 1;
+		} else {
+			printf_ln(_("Patch is empty."));
+			die_user_resolve(state);
+		}
 	}
 
 	strbuf_addstr(&msg, "\n\n");

@@ -1792,6 +1798,9 @@ static void am_run(struct am_state *state, int resume)
 		if (state->interactive && do_interactive(state))
 			goto next;
 
+		if (state->empty_commit)
+			goto commit;
+
 		if (run_applypatch_msg_hook(state))
 			exit(1);
 

@@ -1827,6 +1836,7 @@ static void am_run(struct am_state *state, int resume)
 			die_user_resolve(state);
 		}
 
+commit:
 		do_commit(state);
 
 next:

@@ -2357,6 +2367,10 @@ int cmd_am(int argc, const char **argv, const char *prefix)
 		{ OPTION_STRING, 'S', "gpg-sign", &state.sign_commit, N_("key-id"),
 		  N_("GPG-sign commits"),
 		  PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
+		OPT_BOOL(0, "always", &state.always,
+			N_("always apply patch event if the patch is empty")),
+		OPT_HIDDEN_BOOL(0, "empty-commit", &state.empty_commit,
+			N_("(internal use for skipping git-apply to empty commits)")),
 		OPT_HIDDEN_BOOL(0, "rebasing", &state.rebasing,
 			N_("(internal use for git-rebase)")),
 		OPT_END()

diff --git a/t/t4150-am.sh b/t/t4150-am.sh
index 2aaaa0d7ded..5b3617857a8 100755
--- a/t/t4150-am.sh
+++ b/t/t4150-am.sh

@@ -196,6 +196,12 @@ test_expect_success setup '
 
 	git format-patch -M --stdout lorem^ >rename-add.patch &&
 
+	git checkout -b empty-commit &&
+	git commit -m "empty commit" --allow-empty &&
+
+	git format-patch --stdout empty-commit^ >empty.patch &&
+	git format-patch --always --stdout empty-commit^ >empty-commit.patch &&
+
 	# reset time
 	sane_unset test_tick &&
 	test_tick

@@ -1152,4 +1158,23 @@ test_expect_success 'apply binary blob in partial clone' '
 	git -C client am ../patch
 '
 
+test_expect_success 'am a real empty patch with the --always option' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
+	test_must_fail git am --always empty.patch 2>actual &&
+	echo Patch format detection failed. >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'am a patch with empty commits' '
+	grep "empty commit" empty-commit.patch &&
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
+	git checkout empty-commit^ &&
+	git am --always empty-commit.patch &&
+	test_path_is_missing .git/rebase-apply &&
+	git cat-file commit HEAD >actual &&
+	test_i18ngrep "empty commit" actual
+'
+
 test_done

-- 
gitgitgadget

Am 12.11.21 um 05:58 schrieb Aleen via GitGitGadget:

Since that git has supported the --always option for the git-format-patch
command to create a patch with empty commit message, git-am should support
applying and committing with empty patches.

The symmetry is compelling, but "always" is quite generic.  I can see
e.g. someone expecting "git am --always" to imply --keep-non-patch.

git commit and cherry-pick have --allow-empty, which is (a bit) more
specific.  That seems to me a better option name to copy for a commit-
creating command like git am.

René

Since that git has supported the --always option for the git-format-patch
command to create a patch with empty commit message, git-am should support
applying and committing with empty patches.

Changes since v1:

 * test: am: add the case when not passing the --always option
 * chore: am: rename the --always option to --allow-empty

Aleen (4):
  doc: git-format-patch: specify the option --always
  am: support --always option to am empty commits
  test: am: add the case when not passing the --always option
  chore: am: rename the --always option to --allow-empty

 Documentation/git-am.txt           |  5 +++++
 Documentation/git-format-patch.txt |  5 +++++
 builtin/am.c                       | 18 +++++++++++++--
 t/t4150-am.sh                      | 35 ++++++++++++++++++++++++++++++
 4 files changed, 61 insertions(+), 2 deletions(-)


base-commit: b550198c73edd4cc058832dcf74b41aeec2adba2
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1076%2Faleen42%2Fnext-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1076/aleen42/next-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/1076

Range-diff vs v1:

 1:  71e6989375c = 1:  71e6989375c doc: git-format-patch: specify the option --always
 2:  59b1417da37 = 2:  59b1417da37 am: support --always option to am empty commits
 -:  ----------- > 3:  da024ced668 test: am: add the case when not passing the --always option
 -:  ----------- > 4:  45e9720f40b chore: am: rename the --always option to --allow-empty

-- 
gitgitgadget

From: Aleen <redacted>

Signed-off-by: Aleen <redacted>
---
 Documentation/git-format-patch.txt | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
index 113eabc107c..a9f2bf94182 100644
--- a/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt

@@ -30,6 +30,7 @@ SYNOPSIS
 		   [--range-diff=<previous> [--creation-factor=<percent>]]
 		   [--filename-max-length=<n>]
 		   [--progress]
+		   [--always]
 		   [<common diff options>]
 		   [ <since> | <revision range> ]
 

@@ -388,6 +389,10 @@ you can use `--suffix=-patch` to get `0001-description-of-my-change-patch`.
 --progress::
 	Show progress reports on stderr as patches are generated.
 
+--always::
+	Patch commits with detailed commit messages,
+	even if they emit no changes. (see linkgit:git-diff-tree[1])
+
 CONFIGURATION
 -------------
 You can specify extra mail header lines to be added to each message,

-- 
gitgitgadget

From: Aleen <redacted>

Signed-off-by: Aleen <redacted>
---
 Documentation/git-am.txt |  5 +++++
 builtin/am.c             | 18 ++++++++++++++++--
 t/t4150-am.sh            | 25 +++++++++++++++++++++++++
 3 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/Documentation/git-am.txt b/Documentation/git-am.txt
index 0a4a984dfde..de5d11e404c 100644
--- a/Documentation/git-am.txt
+++ b/Documentation/git-am.txt

@@ -16,6 +16,7 @@ SYNOPSIS
 	 [--exclude=<path>] [--include=<path>] [--reject] [-q | --quiet]
 	 [--[no-]scissors] [-S[<keyid>]] [--patch-format=<format>]
 	 [--quoted-cr=<action>]
+	 [--always]
 	 [(<mbox> | <Maildir>)...]
 'git am' (--continue | --skip | --abort | --quit | --show-current-patch[=(diff|raw)])
 

@@ -159,6 +160,10 @@ default.   You can use `--no-utf8` to override this.
 	countermand both `commit.gpgSign` configuration variable, and
 	earlier `--gpg-sign`.
 
+--always::
+	Apply patches of commits with detailed commit messages,
+	even if they emit no changes. (see linkgit:git-format-patch[1])
+
 --continue::
 -r::
 --resolved::

diff --git a/builtin/am.c b/builtin/am.c
index 8677ea2348a..d11efc16f92 100644
--- a/builtin/am.c
+++ b/builtin/am.c

@@ -124,6 +124,8 @@ struct am_state {
 	int ignore_date;
 	int allow_rerere_autoupdate;
 	const char *sign_commit;
+	int always;
+	int empty_commit;
 	int rebasing;
 };
 

@@ -1249,8 +1251,12 @@ static int parse_mail(struct am_state *state, const char *mail)
 	}
 
 	if (is_empty_or_missing_file(am_path(state, "patch"))) {
-		printf_ln(_("Patch is empty."));
-		die_user_resolve(state);
+		if (state->always) {
+			state->empty_commit = 1;
+		} else {
+			printf_ln(_("Patch is empty."));
+			die_user_resolve(state);
+		}
 	}
 
 	strbuf_addstr(&msg, "\n\n");

@@ -1792,6 +1798,9 @@ static void am_run(struct am_state *state, int resume)
 		if (state->interactive && do_interactive(state))
 			goto next;
 
+		if (state->empty_commit)
+			goto commit;
+
 		if (run_applypatch_msg_hook(state))
 			exit(1);
 

@@ -1827,6 +1836,7 @@ static void am_run(struct am_state *state, int resume)
 			die_user_resolve(state);
 		}
 
+commit:
 		do_commit(state);
 
 next:

@@ -2357,6 +2367,10 @@ int cmd_am(int argc, const char **argv, const char *prefix)
 		{ OPTION_STRING, 'S', "gpg-sign", &state.sign_commit, N_("key-id"),
 		  N_("GPG-sign commits"),
 		  PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
+		OPT_BOOL(0, "always", &state.always,
+			N_("always apply patch event if the patch is empty")),
+		OPT_HIDDEN_BOOL(0, "empty-commit", &state.empty_commit,
+			N_("(internal use for skipping git-apply to empty commits)")),
 		OPT_HIDDEN_BOOL(0, "rebasing", &state.rebasing,
 			N_("(internal use for git-rebase)")),
 		OPT_END()

diff --git a/t/t4150-am.sh b/t/t4150-am.sh
index 2aaaa0d7ded..5b3617857a8 100755
--- a/t/t4150-am.sh
+++ b/t/t4150-am.sh

@@ -196,6 +196,12 @@ test_expect_success setup '
 
 	git format-patch -M --stdout lorem^ >rename-add.patch &&
 
+	git checkout -b empty-commit &&
+	git commit -m "empty commit" --allow-empty &&
+
+	git format-patch --stdout empty-commit^ >empty.patch &&
+	git format-patch --always --stdout empty-commit^ >empty-commit.patch &&
+
 	# reset time
 	sane_unset test_tick &&
 	test_tick

@@ -1152,4 +1158,23 @@ test_expect_success 'apply binary blob in partial clone' '
 	git -C client am ../patch
 '
 
+test_expect_success 'am a real empty patch with the --always option' '
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
+	test_must_fail git am --always empty.patch 2>actual &&
+	echo Patch format detection failed. >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'am a patch with empty commits' '
+	grep "empty commit" empty-commit.patch &&
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
+	git checkout empty-commit^ &&
+	git am --always empty-commit.patch &&
+	test_path_is_missing .git/rebase-apply &&
+	git cat-file commit HEAD >actual &&
+	test_i18ngrep "empty commit" actual
+'
+
 test_done

-- 
gitgitgadget

From: Aleen <redacted>

Signed-off-by: Aleen <redacted>
---
 t/t4150-am.sh | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/t/t4150-am.sh b/t/t4150-am.sh
index 5b3617857a8..364c61ba198 100755
--- a/t/t4150-am.sh
+++ b/t/t4150-am.sh

@@ -1166,7 +1166,17 @@ test_expect_success 'am a real empty patch with the --always option' '
 	test_cmp expected actual
 '
 
-test_expect_success 'am a patch with empty commits' '
+test_expect_success 'am a patch of empty commits without the --always option' '
+	grep "empty commit" empty-commit.patch &&
+	rm -fr .git/rebase-apply &&
+	git reset --hard &&
+	git checkout empty-commit^ &&
+	test_must_fail git am empty-commit.patch >err &&
+	test_path_is_dir .git/rebase-apply &&
+	test_i18ngrep "Patch is empty." err
+'
+
+test_expect_success 'am a patch of empty commits with the --always option' '
 	grep "empty commit" empty-commit.patch &&
 	rm -fr .git/rebase-apply &&
 	git reset --hard &&

-- 
gitgitgadget

From: Aleen <redacted>

Signed-off-by: Aleen <redacted>
---
 Documentation/git-am.txt |  4 ++--
 builtin/am.c             |  8 ++++----
 t/t4150-am.sh            | 10 +++++-----
 3 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/Documentation/git-am.txt b/Documentation/git-am.txt
index de5d11e404c..6ed844af9c6 100644
--- a/Documentation/git-am.txt
+++ b/Documentation/git-am.txt

@@ -16,7 +16,7 @@ SYNOPSIS
 	 [--exclude=<path>] [--include=<path>] [--reject] [-q | --quiet]
 	 [--[no-]scissors] [-S[<keyid>]] [--patch-format=<format>]
 	 [--quoted-cr=<action>]
-	 [--always]
+	 [--allow-empty]
 	 [(<mbox> | <Maildir>)...]
 'git am' (--continue | --skip | --abort | --quit | --show-current-patch[=(diff|raw)])
 

@@ -160,7 +160,7 @@ default.   You can use `--no-utf8` to override this.
 	countermand both `commit.gpgSign` configuration variable, and
 	earlier `--gpg-sign`.
 
---always::
+--allow-empty::
 	Apply patches of commits with detailed commit messages,
 	even if they emit no changes. (see linkgit:git-format-patch[1])
 

diff --git a/builtin/am.c b/builtin/am.c
index d11efc16f92..a8661098acf 100644
--- a/builtin/am.c
+++ b/builtin/am.c

@@ -124,7 +124,7 @@ struct am_state {
 	int ignore_date;
 	int allow_rerere_autoupdate;
 	const char *sign_commit;
-	int always;
+	int allow_empty;
 	int empty_commit;
 	int rebasing;
 };

@@ -1251,7 +1251,7 @@ static int parse_mail(struct am_state *state, const char *mail)
 	}
 
 	if (is_empty_or_missing_file(am_path(state, "patch"))) {
-		if (state->always) {
+		if (state->allow_empty) {
 			state->empty_commit = 1;
 		} else {
 			printf_ln(_("Patch is empty."));

@@ -2367,8 +2367,8 @@ int cmd_am(int argc, const char **argv, const char *prefix)
 		{ OPTION_STRING, 'S', "gpg-sign", &state.sign_commit, N_("key-id"),
 		  N_("GPG-sign commits"),
 		  PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
-		OPT_BOOL(0, "always", &state.always,
-			N_("always apply patch event if the patch is empty")),
+		OPT_BOOL(0, "allow-empty", &state.allow_empty,
+			N_("allow to apply patches of empty commits")),
 		OPT_HIDDEN_BOOL(0, "empty-commit", &state.empty_commit,
 			N_("(internal use for skipping git-apply to empty commits)")),
 		OPT_HIDDEN_BOOL(0, "rebasing", &state.rebasing,

diff --git a/t/t4150-am.sh b/t/t4150-am.sh
index 364c61ba198..b47a0fa41e7 100755
--- a/t/t4150-am.sh
+++ b/t/t4150-am.sh

@@ -1158,15 +1158,15 @@ test_expect_success 'apply binary blob in partial clone' '
 	git -C client am ../patch
 '
 
-test_expect_success 'am a real empty patch with the --always option' '
+test_expect_success 'am a real empty patch with the --allow-empty option' '
 	rm -fr .git/rebase-apply &&
 	git reset --hard &&
-	test_must_fail git am --always empty.patch 2>actual &&
+	test_must_fail git am --allow-empty empty.patch 2>actual &&
 	echo Patch format detection failed. >expected &&
 	test_cmp expected actual
 '
 
-test_expect_success 'am a patch of empty commits without the --always option' '
+test_expect_success 'am a patch of empty commits without the --allow-empty option' '
 	grep "empty commit" empty-commit.patch &&
 	rm -fr .git/rebase-apply &&
 	git reset --hard &&

@@ -1176,12 +1176,12 @@ test_expect_success 'am a patch of empty commits without the --always option' '
 	test_i18ngrep "Patch is empty." err
 '
 
-test_expect_success 'am a patch of empty commits with the --always option' '
+test_expect_success 'am a patch of empty commits with the --allow-empty option' '
 	grep "empty commit" empty-commit.patch &&
 	rm -fr .git/rebase-apply &&
 	git reset --hard &&
 	git checkout empty-commit^ &&
-	git am --always empty-commit.patch &&
+	git am --allow-empty empty-commit.patch &&
 	test_path_is_missing .git/rebase-apply &&
 	git cat-file commit HEAD >actual &&
 	test_i18ngrep "empty commit" actual

-- 
gitgitgadget

Dears René,

The symmetry is compelling, but "always" is quite generic.  I can see
e.g. someone expecting "git am --always" to imply --keep-non-patch.

git commit and cherry-pick have --allow-empty, which is (a bit) more
specific.  That seems to me a better option name to copy for a commit-
creating command like git am.

It was designed corresponding to --always option in git-format-patch, which
will be pssed into git-diff-tree. As a commit-creating command, --allow-empty
is apparently a better choice. I will re-submit it, thank you.

"Aleen via GitGitGadget" [off-list ref] writes:

From: Aleen <redacted>
Subject: Re: [PATCH v2 1/4] doc: git-format-patch: specify the option --always

"specify" -> "describe", perhaps?

What does the verb "Patch" mean here?  It cannot be what the command
"patch" does, i.e. apply a diff to working tree files, as
format-patch does not apply any patch.  

Who guarantees that commit messages are detailed?  If I write a
commit that does not change anything with a one-liner message, would
this option make that message more detailed?  I doubt that it would
be the case.

This option may sit much better near the --ignore-if-in-upstream
option.  The primary way the command is told which commits to show
is via its argument (<since> or <revision-range>), and we do not
have many options to affect the selection of commits, but this one
and --ignore-if-in-upstream are such options.  Borrowing from the
way the description of that other option is phrased, perhaps

    Include patches for commits that do not introduce any change,
    which are omitted by default.

Do not refer to 'git-diff-tree'; I do not think the reader who is
learning how to drive format-patch will learn anything new by
reading that page.

I have a feeling that if we were to endorse and promote this option
by documenting (note: it was an accident and a mistake that this
option is understood by underlying revision.c parse machinery, and
not a designed behaviour for format-patch to do anything to empty
commits), we should give users a better synonym to invoke it, but
that can and should be outside of this step.

"Aleen via GitGitGadget" [off-list ref] writes:

From: Aleen <redacted>
Subject: Re: [PATCH v2 2/4] am: support --always option to am empty commits

As the inventor of "format-patch" and "am", I probably should wish
that "to am" were by now a valid verb, but no, it is not.

More importantly, when an empty patch comes, there can be many
different ways for the "am" command to handle it.  "to am empty
commits" does not say how the patch chooses to so and does not make
a very useful title for this commit.

Right now, we error out, simply because it is an easy mistake to
save a non-patch e-mail to the mailbox when intending to save a
series of patches belonging to a topic, and the user is expected to
say "git am --skip" to skip over it when it happens.  The above
"Subject:" can be read to mean that the new option instead allows
such an empty message to be skipped without stopping and forcing the
user to say "am --skip", which may be a useful thing to do.  Or it
may mean that the new option creates an empty commit, using the
contents of the e-mail as the commit log message.  Does this patch
offer both behaviour?  If so, "to am", even though it does not
convey a bit of information, might be an acceptable compromise.  If
the patch implements only one of the behaviours, then we should say
so.  Either one of these two:

    am: --always option skips empty patches
    am: --always option records empty patches as empty commits

Also, I thought that the previous round saw a conclusion that --always
is a bad name for the option.  If we are making the second round,
let's not start with a bad name and the "fix the mistake" of
starting with a bad name in a later step.  Just start with the final
name from the beginning.

+--always::
+	Apply patches of commits with detailed commit messages,
+	even if they emit no changes. (see linkgit:git-format-patch[1])

Almost the same comment as 1/4 applies to the above description.

    --empty-patch=(skip|asis|die)::
	The command usually errors out when seeing an input e-mail
	message that lacks a patch.  When this option is set to
	'skip', skip such an e-mail message without erroring out.
	When this option is set to 'asis', create an empty commit,
	recording the contents of the e-mail message as its log.
	'die' is the default.


perhaps?  Assuming that 'skip' would make a useful addition to the
mix in the future.

OK, so here is where the parse_options() records the command line
option.

+	int empty_commit;

I do not think this addtion of empty_commit member to this structure
is welcome or necessary.

 	int rebasing;
 };

 	if (is_empty_or_missing_file(am_path(state, "patch"))) {
-		printf_ln(_("Patch is empty."));
-		die_user_resolve(state);
+		if (state->always) {
+			state->empty_commit = 1;
+		} else {
+			printf_ln(_("Patch is empty."));
+			die_user_resolve(state);
+		}
 	}

I am only thinking aloud, but I suspect that the whole "if 'patch'
is empty, do something special" code logically belongs to the
caller.  Perhaps we should remove this block altogether and let the
code continue the rest of this function.  And return 0, as this is
not like mail-system-internal-data that we want to pretend did not
even exist, and have the caller check if "patch" file is empty and
act accordingly.

This is probably a wrong place to jump from.  You are bypassing
applypatch-msg-hook that may be serving as a gate to catch typos
if you are going to create a commit.

So, perhaps check if "patch" is empty here, using the code you'd
lift from parse_mail(), and if it is empty then:

  - if --empty-commit is set to die (or left default), do the
    printf_ln(_("Patch is empty.")) followed by a call to
    die_user_resolve(state), just like before.

  - if it is set to skip, jump to "next", just like when
    parse_mail() returned 1.

  - otherwise (i.e. you are told to create an empty commit),
    remember the fact that current e-mail has no patch, but continue
    to the next step to run the hook.

 		if (run_applypatch_msg_hook(state))
 			exit(1);

And after passing the hook, if your earlier check says that there is
no patch and you are to create an empty commit, jump to "commit"
label from here.

What is this one about?  If this is trying to clean up the cruft the
previous step made, it may be better to do the clean-up in the
previous step using test_when_finished.

+	git reset --hard &&
+	test_must_fail git am --always empty.patch 2>actual &&
+	echo Patch format detection failed. >expected &&
+	test_cmp expected actual
+'

It is curious that the error message the patch touched said "Patch
is empty." but the test checks for a different message.  Are we
testing the right failure mode?

+test_expect_success 'am a patch with empty commits' '
+	grep "empty commit" empty-commit.patch &&

What is this testing?  If it is checking the sanity of test data we
created earlier, shouldn't we do so where we generated the data
(i.e. the "setup" block that we earlier saw)?

+	rm -fr .git/rebase-apply &&
+	git reset --hard &&

These are trying to clean up the cruft the previous step (added by
this patch) may have left.  Perhaps these should be done inside
test_when_finished of the previous step?

+	git checkout empty-commit^ &&
+	git am --always empty-commit.patch &&
+	test_path_is_missing .git/rebase-apply &&

We should trust "git am"'s exit status here, I would think, rather
than be so intimate with the internal implementation detail like the
name of the temporary directory the command uses.

+	git cat-file commit HEAD >actual &&
+	test_i18ngrep "empty commit" actual

test_i18ngrep -> grep

The input (i.e. the commit that resulted in this empty patch) said.
"empty commit", and we are making sure that string appears, but we
are not making sure that is the only string appears in the log
message.  Is it because we will later enhance the command to
automatically extend the single-liner "empty patch" log message into
a lot more detailed one?  I doubt it ;-)

More importantly, the above checks if (part of) the log message is
recorded, but does not check if the resulting commit is what is
expected, i.e. an empty one.

Perhaps checking with "grep" is way too loose a test.  Shouldn't we
do something like

	git show -1 --format='%B' >actual

and compare it with expected "the log is recorded as-is, and there
is no change between HEAD^ and HEAD"?

+'
+
 test_done

Thanks.

Since that git has supported the --always option for the git-format-patch
command to create a patch with an empty commit message, git-am should
support applying and committing with empty patches.

----------------------------------------------------------------------------

Changes since v1:

 1. add a case when not passing the --always option
 2. rename the --always option to --allow-empty

----------------------------------------------------------------------------

Changes since v2:

 1. rename the --allow-empty option to --empty-commit
 2. introduce three different strategies (die|skip|asis) when trying to
    record empty patches as empty commits.

----------------------------------------------------------------------------

Aleen (2):
  doc: git-format-patch: describe the option --always
  am: support --empty-commit option to handle empty patches

 Documentation/git-am.txt           |  9 +++++
 Documentation/git-format-patch.txt |  6 +++-
 builtin/am.c                       | 48 ++++++++++++++++++++++---
 t/t4150-am.sh                      | 58 ++++++++++++++++++++++++++++++
 4 files changed, 115 insertions(+), 6 deletions(-)


base-commit: b550198c73edd4cc058832dcf74b41aeec2adba2
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1076%2Faleen42%2Fnext-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1076/aleen42/next-v3
Pull-Request: https://github.com/gitgitgadget/git/pull/1076

Range-diff vs v2:

 1:  71e6989375c ! 1:  9f1b3dd6d0b doc: git-format-patch: specify the option --always
     @@ Metadata
      Author: Aleen [off-list ref]
      
       ## Commit message ##
     -    doc: git-format-patch: specify the option --always
     +    doc: git-format-patch: describe the option --always
      
          Signed-off-by: Aleen [off-list ref]
      
       ## Documentation/git-format-patch.txt ##
      @@ Documentation/git-format-patch.txt: SYNOPSIS
     - 		   [--range-diff=<previous> [--creation-factor=<percent>]]
     - 		   [--filename-max-length=<n>]
     - 		   [--progress]
     -+		   [--always]
     - 		   [<common diff options>]
     - 		   [ <since> | <revision range> ]
     - 
     -@@ Documentation/git-format-patch.txt: you can use `--suffix=-patch` to get `0001-description-of-my-change-patch`.
     - --progress::
     - 	Show progress reports on stderr as patches are generated.
     + 		   [-n | --numbered | -N | --no-numbered]
     + 		   [--start-number <n>] [--numbered-files]
     + 		   [--in-reply-to=<message id>] [--suffix=.<sfx>]
     +-		   [--ignore-if-in-upstream]
     ++		   [--ignore-if-in-upstream] [--always]
     + 		   [--cover-from-description=<mode>]
     + 		   [--rfc] [--subject-prefix=<subject prefix>]
     + 		   [(--reroll-count|-v) <n>]
     +@@ Documentation/git-format-patch.txt: will want to ensure that threading is disabled for `git send-email`.
     + 	patches being generated, and any patch that matches is
     + 	ignored.
       
      +--always::
     -+	Patch commits with detailed commit messages,
     -+	even if they emit no changes. (see linkgit:git-diff-tree[1])
     ++	Include patches for commits that do not introduce any change,
     ++	which are omitted by default.
      +
     - CONFIGURATION
     - -------------
     - You can specify extra mail header lines to be added to each message,
     + --cover-from-description=<mode>::
     + 	Controls which parts of the cover letter will be automatically
     + 	populated using the branch's description.
 2:  59b1417da37 ! 2:  ef33ce8c6f9 am: support --always option to am empty commits
     @@ Metadata
      Author: Aleen [off-list ref]
      
       ## Commit message ##
     -    am: support --always option to am empty commits
     +    am: support --empty-commit option to handle empty patches
      
          Signed-off-by: Aleen [off-list ref]
      
     @@ Documentation/git-am.txt: SYNOPSIS
       	 [--exclude=<path>] [--include=<path>] [--reject] [-q | --quiet]
       	 [--[no-]scissors] [-S[<keyid>]] [--patch-format=<format>]
       	 [--quoted-cr=<action>]
     -+	 [--always]
     ++	 [--empty-commit=(die|skip|asis)]
       	 [(<mbox> | <Maildir>)...]
       'git am' (--continue | --skip | --abort | --quit | --show-current-patch[=(diff|raw)])
       
     -@@ Documentation/git-am.txt: default.   You can use `--no-utf8` to override this.
     - 	countermand both `commit.gpgSign` configuration variable, and
     - 	earlier `--gpg-sign`.
     +@@ Documentation/git-am.txt: OPTIONS
     + --quoted-cr=<action>::
     + 	This flag will be passed down to 'git mailinfo' (see linkgit:git-mailinfo[1]).
       
     -+--always::
     -+	Apply patches of commits with detailed commit messages,
     -+	even if they emit no changes. (see linkgit:git-format-patch[1])
     ++--empty-commit=(die|skip|asis)::
     ++	The command usually errors out when seeing an input e-mail
     ++	message that lacks a patch. When this option is set to
     ++	'skip', skip such an e-mail message without outputting error.
     ++	When this option is set to 'asis', create an empty commit,
     ++	recording the contents of the e-mail message as its log.
     ++	'die' is specified by default.
      +
     - --continue::
     - -r::
     - --resolved::
     + -m::
     + --message-id::
     + 	Pass the `-m` flag to 'git mailinfo' (see linkgit:git-mailinfo[1]),
      
       ## builtin/am.c ##
     -@@ builtin/am.c: struct am_state {
     - 	int ignore_date;
     - 	int allow_rerere_autoupdate;
     - 	const char *sign_commit;
     -+	int always;
     -+	int empty_commit;
     - 	int rebasing;
     +@@ builtin/am.c: enum show_patch_type {
     + 	SHOW_PATCH_DIFF = 1,
       };
       
     ++enum empty_commit_action {
     ++	DIE_EMPTY_COMMIT = 0,  /* output errors */
     ++	SKIP_EMPTY_COMMIT,     /* skip without outputting errors */
     ++	ASIS_EMPTY_COMMIT      /* keep recording as empty commits */
     ++};
     ++
     + struct am_state {
     + 	/* state directory path */
     + 	char *dir;
     +@@ builtin/am.c: struct am_state {
     + 	int message_id;
     + 	int scissors; /* enum scissors_type */
     + 	int quoted_cr; /* enum quoted_cr_action */
     ++	int empty_commit; /* enum empty_commit_action */
     + 	struct strvec git_apply_opts;
     + 	const char *resolvemsg;
     + 	int committer_date_is_author_date;
     +@@ builtin/am.c: static int am_option_parse_quoted_cr(const struct option *opt,
     + 	return 0;
     + }
     + 
     ++static int am_option_parse_empty_commit(const struct option *opt,
     ++				     const char *arg, int unset)
     ++{
     ++	int *opt_value = opt->value;
     ++
     ++	if (unset || !strcmp(arg, "die"))
     ++		*opt_value = DIE_EMPTY_COMMIT;
     ++	else if (!strcmp(arg, "skip"))
     ++		*opt_value = SKIP_EMPTY_COMMIT;
     ++	else if (!strcmp(arg, "asis"))
     ++		*opt_value = ASIS_EMPTY_COMMIT;
     ++	else
     ++		return error(_("Invalid value for --empty-commit: %s"), arg);
     ++
     ++	return 0;
     ++}
     ++
     + /**
     +  * Returns path relative to the am_state directory.
     +  */
      @@ builtin/am.c: static int parse_mail(struct am_state *state, const char *mail)
     + 		goto finish;
       	}
       
     - 	if (is_empty_or_missing_file(am_path(state, "patch"))) {
     +-	if (is_empty_or_missing_file(am_path(state, "patch"))) {
      -		printf_ln(_("Patch is empty."));
      -		die_user_resolve(state);
     -+		if (state->always) {
     -+			state->empty_commit = 1;
     -+		} else {
     -+			printf_ln(_("Patch is empty."));
     -+			die_user_resolve(state);
     -+		}
     - 	}
     - 
     +-	}
     +-
       	strbuf_addstr(&msg, "\n\n");
     + 	strbuf_addbuf(&msg, &mi.log_message);
     + 	strbuf_stripspace(&msg, 0);
      @@ builtin/am.c: static void am_run(struct am_state *state, int resume)
       		if (state->interactive && do_interactive(state))
       			goto next;
       
     -+		if (state->empty_commit)
     -+			goto commit;
     ++		if (is_empty_or_missing_file(am_path(state, "patch"))) {
     ++			if (state->empty_commit == SKIP_EMPTY_COMMIT)
     ++				goto next;
     ++			else if (state->empty_commit == ASIS_EMPTY_COMMIT) {
     ++				if (run_applypatch_msg_hook(state))
     ++					exit(1);
     ++				else
     ++					goto commit;
     ++			} else if (state->empty_commit == DIE_EMPTY_COMMIT) {
     ++				printf_ln(_("Patch is empty."));
     ++				die_user_resolve(state);
     ++			}
     ++		}
      +
       		if (run_applypatch_msg_hook(state))
       			exit(1);
     @@ builtin/am.c: int cmd_am(int argc, const char **argv, const char *prefix)
       		{ OPTION_STRING, 'S', "gpg-sign", &state.sign_commit, N_("key-id"),
       		  N_("GPG-sign commits"),
       		  PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
     -+		OPT_BOOL(0, "always", &state.always,
     -+			N_("always apply patch event if the patch is empty")),
     -+		OPT_HIDDEN_BOOL(0, "empty-commit", &state.empty_commit,
     -+			N_("(internal use for skipping git-apply to empty commits)")),
     ++		{ OPTION_CALLBACK, 0, "empty-commit", &state.empty_commit,
     ++		  "(die|skip|asis)",
     ++		  N_("specify how to handle empty patches"),
     ++		  PARSE_OPT_OPTARG, am_option_parse_empty_commit },
       		OPT_HIDDEN_BOOL(0, "rebasing", &state.rebasing,
       			N_("(internal use for git-rebase)")),
       		OPT_END()
     @@ t/t4150-am.sh: test_expect_success 'apply binary blob in partial clone' '
       	git -C client am ../patch
       '
       
     -+test_expect_success 'am a real empty patch with the --always option' '
     -+	rm -fr .git/rebase-apply &&
     -+	git reset --hard &&
     -+	test_must_fail git am --always empty.patch 2>actual &&
     ++test_expect_success 'still output error with --empty-commit when meeting empty files' '
     ++	test_must_fail git am --empty-commit=skip empty.patch 2>actual &&
      +	echo Patch format detection failed. >expected &&
      +	test_cmp expected actual
      +'
      +
     -+test_expect_success 'am a patch with empty commits' '
     -+	grep "empty commit" empty-commit.patch &&
     -+	rm -fr .git/rebase-apply &&
     -+	git reset --hard &&
     ++test_expect_success 'error when meeting e-mail message that lacks a patch by default' '
      +	git checkout empty-commit^ &&
     -+	git am --always empty-commit.patch &&
     ++	test_must_fail git am empty-commit.patch >err &&
     ++	test_path_is_dir .git/rebase-apply &&
     ++	test_i18ngrep "Patch is empty." err &&
     ++	rm -fr .git/rebase-apply &&
     ++
     ++	test_must_fail git am --empty-commit=die empty-commit.patch >err &&
     ++	test_path_is_dir .git/rebase-apply &&
     ++	test_i18ngrep "Patch is empty." err &&
     ++	rm -fr .git/rebase-apply &&
     ++
     ++	test_must_fail git am --empty-commit=die cover-letter.patch >err &&
     ++	test_path_is_dir .git/rebase-apply &&
     ++	test_i18ngrep "Patch is empty." err &&
     ++	rm -fr .git/rebase-apply
     ++'
     ++
     ++test_expect_success 'skip without error when meeting e-mail message that lacks a patch' '
     ++	git am --empty-commit=skip empty-commit.patch >err &&
     ++	test_path_is_missing .git/rebase-apply &&
     ++	git rev-parse empty-commit^ >expected &&
     ++	git rev-parse HEAD >actual &&
     ++	test_cmp expected actual &&
     ++
     ++	git am --empty-commit=skip cover-letter.patch >err &&
     ++	test_path_is_missing .git/rebase-apply &&
     ++	git rev-parse empty-commit^ >expected &&
     ++	git rev-parse HEAD >actual &&
     ++	test_cmp expected actual
     ++'
     ++
     ++test_expect_success 'record as an empty commit when meeting e-mail message that lacks a patch' '
     ++	git am --empty-commit=asis empty-commit.patch &&
     ++	test_path_is_missing .git/rebase-apply &&
     ++	git show empty-commit --format="%B" >expected &&
     ++	git show HEAD --format="%B" >actual &&
     ++	grep -f actual expected &&
     ++
     ++	git am --empty-commit=asis cover-letter.patch &&
      +	test_path_is_missing .git/rebase-apply &&
     -+	git cat-file commit HEAD >actual &&
     -+	test_i18ngrep "empty commit" actual
     ++	git show empty-commit --format="%B" >expected &&
     ++	git show HEAD --format="%B" >actual &&
     ++	grep -f actual expected
      +'
      +
       test_done
 3:  da024ced668 < -:  ----------- test: am: add the case when not passing the --always option
 4:  45e9720f40b < -:  ----------- chore: am: rename the --always option to --allow-empty

-- 
gitgitgadget

From: Aleen <redacted>

Signed-off-by: Aleen <redacted>
---
 Documentation/git-format-patch.txt | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
index 113eabc107c..be797d7a28f 100644
--- a/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt

@@ -18,7 +18,7 @@ SYNOPSIS
 		   [-n | --numbered | -N | --no-numbered]
 		   [--start-number <n>] [--numbered-files]
 		   [--in-reply-to=<message id>] [--suffix=.<sfx>]
-		   [--ignore-if-in-upstream]
+		   [--ignore-if-in-upstream] [--always]
 		   [--cover-from-description=<mode>]
 		   [--rfc] [--subject-prefix=<subject prefix>]
 		   [(--reroll-count|-v) <n>]

@@ -192,6 +192,10 @@ will want to ensure that threading is disabled for `git send-email`.
 	patches being generated, and any patch that matches is
 	ignored.
 
+--always::
+	Include patches for commits that do not introduce any change,
+	which are omitted by default.
+
 --cover-from-description=<mode>::
 	Controls which parts of the cover letter will be automatically
 	populated using the branch's description.

-- 
gitgitgadget

From: Aleen <redacted>

Signed-off-by: Aleen <redacted>
---
 Documentation/git-am.txt |  9 +++++++
 builtin/am.c             | 48 +++++++++++++++++++++++++++++----
 t/t4150-am.sh            | 58 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 110 insertions(+), 5 deletions(-)

diff --git a/Documentation/git-am.txt b/Documentation/git-am.txt
index 0a4a984dfde..d8d3bf202d7 100644
--- a/Documentation/git-am.txt
+++ b/Documentation/git-am.txt

@@ -16,6 +16,7 @@ SYNOPSIS
 	 [--exclude=<path>] [--include=<path>] [--reject] [-q | --quiet]
 	 [--[no-]scissors] [-S[<keyid>]] [--patch-format=<format>]
 	 [--quoted-cr=<action>]
+	 [--empty-commit=(die|skip|asis)]
 	 [(<mbox> | <Maildir>)...]
 'git am' (--continue | --skip | --abort | --quit | --show-current-patch[=(diff|raw)])
 

@@ -63,6 +64,14 @@ OPTIONS
 --quoted-cr=<action>::
 	This flag will be passed down to 'git mailinfo' (see linkgit:git-mailinfo[1]).
 
+--empty-commit=(die|skip|asis)::
+	The command usually errors out when seeing an input e-mail
+	message that lacks a patch. When this option is set to
+	'skip', skip such an e-mail message without outputting error.
+	When this option is set to 'asis', create an empty commit,
+	recording the contents of the e-mail message as its log.
+	'die' is specified by default.
+
 -m::
 --message-id::
 	Pass the `-m` flag to 'git mailinfo' (see linkgit:git-mailinfo[1]),

diff --git a/builtin/am.c b/builtin/am.c
index 8677ea2348a..e7755c1377e 100644
--- a/builtin/am.c
+++ b/builtin/am.c

@@ -87,6 +87,12 @@ enum show_patch_type {
 	SHOW_PATCH_DIFF = 1,
 };
 
+enum empty_commit_action {
+	DIE_EMPTY_COMMIT = 0,  /* output errors */
+	SKIP_EMPTY_COMMIT,     /* skip without outputting errors */
+	ASIS_EMPTY_COMMIT      /* keep recording as empty commits */
+};
+
 struct am_state {
 	/* state directory path */
 	char *dir;

@@ -118,6 +124,7 @@ struct am_state {
 	int message_id;
 	int scissors; /* enum scissors_type */
 	int quoted_cr; /* enum quoted_cr_action */
+	int empty_commit; /* enum empty_commit_action */
 	struct strvec git_apply_opts;
 	const char *resolvemsg;
 	int committer_date_is_author_date;

@@ -178,6 +185,23 @@ static int am_option_parse_quoted_cr(const struct option *opt,
 	return 0;
 }
 
+static int am_option_parse_empty_commit(const struct option *opt,
+				     const char *arg, int unset)
+{
+	int *opt_value = opt->value;
+
+	if (unset || !strcmp(arg, "die"))
+		*opt_value = DIE_EMPTY_COMMIT;
+	else if (!strcmp(arg, "skip"))
+		*opt_value = SKIP_EMPTY_COMMIT;
+	else if (!strcmp(arg, "asis"))
+		*opt_value = ASIS_EMPTY_COMMIT;
+	else
+		return error(_("Invalid value for --empty-commit: %s"), arg);
+
+	return 0;
+}
+
 /**
  * Returns path relative to the am_state directory.
  */

@@ -1248,11 +1272,6 @@ static int parse_mail(struct am_state *state, const char *mail)
 		goto finish;
 	}
 
-	if (is_empty_or_missing_file(am_path(state, "patch"))) {
-		printf_ln(_("Patch is empty."));
-		die_user_resolve(state);
-	}
-
 	strbuf_addstr(&msg, "\n\n");
 	strbuf_addbuf(&msg, &mi.log_message);
 	strbuf_stripspace(&msg, 0);

@@ -1792,6 +1811,20 @@ static void am_run(struct am_state *state, int resume)
 		if (state->interactive && do_interactive(state))
 			goto next;
 
+		if (is_empty_or_missing_file(am_path(state, "patch"))) {
+			if (state->empty_commit == SKIP_EMPTY_COMMIT)
+				goto next;
+			else if (state->empty_commit == ASIS_EMPTY_COMMIT) {
+				if (run_applypatch_msg_hook(state))
+					exit(1);
+				else
+					goto commit;
+			} else if (state->empty_commit == DIE_EMPTY_COMMIT) {
+				printf_ln(_("Patch is empty."));
+				die_user_resolve(state);
+			}
+		}
+
 		if (run_applypatch_msg_hook(state))
 			exit(1);
 

@@ -1827,6 +1860,7 @@ static void am_run(struct am_state *state, int resume)
 			die_user_resolve(state);
 		}
 
+commit:
 		do_commit(state);
 
 next:

@@ -2357,6 +2391,10 @@ int cmd_am(int argc, const char **argv, const char *prefix)
 		{ OPTION_STRING, 'S', "gpg-sign", &state.sign_commit, N_("key-id"),
 		  N_("GPG-sign commits"),
 		  PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
+		{ OPTION_CALLBACK, 0, "empty-commit", &state.empty_commit,
+		  "(die|skip|asis)",
+		  N_("specify how to handle empty patches"),
+		  PARSE_OPT_OPTARG, am_option_parse_empty_commit },
 		OPT_HIDDEN_BOOL(0, "rebasing", &state.rebasing,
 			N_("(internal use for git-rebase)")),
 		OPT_END()

diff --git a/t/t4150-am.sh b/t/t4150-am.sh
index 2aaaa0d7ded..13fdf2f86c6 100755
--- a/t/t4150-am.sh
+++ b/t/t4150-am.sh

@@ -196,6 +196,12 @@ test_expect_success setup '
 
 	git format-patch -M --stdout lorem^ >rename-add.patch &&
 
+	git checkout -b empty-commit &&
+	git commit -m "empty commit" --allow-empty &&
+
+	git format-patch --stdout empty-commit^ >empty.patch &&
+	git format-patch --always --stdout empty-commit^ >empty-commit.patch &&
+
 	# reset time
 	sane_unset test_tick &&
 	test_tick

@@ -1152,4 +1158,56 @@ test_expect_success 'apply binary blob in partial clone' '
 	git -C client am ../patch
 '
 
+test_expect_success 'still output error with --empty-commit when meeting empty files' '
+	test_must_fail git am --empty-commit=skip empty.patch 2>actual &&
+	echo Patch format detection failed. >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'error when meeting e-mail message that lacks a patch by default' '
+	git checkout empty-commit^ &&
+	test_must_fail git am empty-commit.patch >err &&
+	test_path_is_dir .git/rebase-apply &&
+	test_i18ngrep "Patch is empty." err &&
+	rm -fr .git/rebase-apply &&
+
+	test_must_fail git am --empty-commit=die empty-commit.patch >err &&
+	test_path_is_dir .git/rebase-apply &&
+	test_i18ngrep "Patch is empty." err &&
+	rm -fr .git/rebase-apply &&
+
+	test_must_fail git am --empty-commit=die cover-letter.patch >err &&
+	test_path_is_dir .git/rebase-apply &&
+	test_i18ngrep "Patch is empty." err &&
+	rm -fr .git/rebase-apply
+'
+
+test_expect_success 'skip without error when meeting e-mail message that lacks a patch' '
+	git am --empty-commit=skip empty-commit.patch >err &&
+	test_path_is_missing .git/rebase-apply &&
+	git rev-parse empty-commit^ >expected &&
+	git rev-parse HEAD >actual &&
+	test_cmp expected actual &&
+
+	git am --empty-commit=skip cover-letter.patch >err &&
+	test_path_is_missing .git/rebase-apply &&
+	git rev-parse empty-commit^ >expected &&
+	git rev-parse HEAD >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'record as an empty commit when meeting e-mail message that lacks a patch' '
+	git am --empty-commit=asis empty-commit.patch &&
+	test_path_is_missing .git/rebase-apply &&
+	git show empty-commit --format="%B" >expected &&
+	git show HEAD --format="%B" >actual &&
+	grep -f actual expected &&
+
+	git am --empty-commit=asis cover-letter.patch &&
+	test_path_is_missing .git/rebase-apply &&
+	git show empty-commit --format="%B" >expected &&
+	git show HEAD --format="%B" >actual &&
+	grep -f actual expected
+'
+
 test_done

-- 
gitgitgadget

Dears Hamano,

Sorry about the late submission, and I have modified it to support the `--empty-commit=(die|skip|asis)` pattern.

+test_expect_success 'record as an empty commit when meeting e-mail message that lacks a patch' '
+	git am --empty-commit=asis empty-commit.patch &&
+	test_path_is_missing .git/rebase-apply &&
+	git show empty-commit --format="%B" >expected &&
+	git show HEAD --format="%B" >actual &&
+	grep -f actual expected &&
+
+	git am --empty-commit=asis cover-letter.patch &&
+	test_path_is_missing .git/rebase-apply &&
+	git show empty-commit --format="%B" >expected &&
+	git show HEAD --format="%B" >actual &&
+	grep -f actual expected
+'

When it comes to the last test case, there are some accidental contents recognized as commit messages inside an empty patch, like:

1. version signatures:
  > -- 
  > 2.34.0.rc2.390.gef33ce8c6f
2. information of cover letter:
  > *** BLURB HERE ***
  >
  > A U Thor (1):
  >   empty commit

I don't think it is necessary to fix it within `mailinfo.c`. Can you give me some suggestions on whether this case should be handled?

Aleen

Since that git has supported the --always option for the git-format-patch
command to create a patch with an empty commit message, git-am should
support applying and committing with empty patches.

----------------------------------------------------------------------------

Changes since v1:

 1. add a case when not passing the --always option
 2. rename the --always option to --allow-empty

----------------------------------------------------------------------------

Changes since v2:

 1. rename the --allow-empty option to --empty-commit
 2. introduce three different strategies (die|skip|asis) when trying to
    record empty patches as empty commits.

----------------------------------------------------------------------------

Changes since v3:

 1. generate the missed file for test cases
 2. grep -f cannot be used under Mac OS

----------------------------------------------------------------------------

Aleen (2):
  doc: git-format-patch: describe the option --always
  am: support --empty-commit option to handle empty patches

 Documentation/git-am.txt           |  9 ++++
 Documentation/git-format-patch.txt |  6 ++-
 builtin/am.c                       | 48 ++++++++++++++++++--
 t/t4150-am.sh                      | 73 ++++++++++++++++++++++++++++++
 4 files changed, 130 insertions(+), 6 deletions(-)


base-commit: b550198c73edd4cc058832dcf74b41aeec2adba2
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1076%2Faleen42%2Fnext-v4
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1076/aleen42/next-v4
Pull-Request: https://github.com/gitgitgadget/git/pull/1076

Range-diff vs v3:

 1:  9f1b3dd6d0b = 1:  9f1b3dd6d0b doc: git-format-patch: describe the option --always
 2:  ef33ce8c6f9 ! 2:  b7e30c9b7ab am: support --empty-commit option to handle empty patches
     @@ t/t4150-am.sh: test_expect_success setup '
      +	git commit -m "empty commit" --allow-empty &&
      +
      +	git format-patch --stdout empty-commit^ >empty.patch &&
     ++	git format-patch --stdout --cover-letter empty-commit^ >cover-letter.patch &&
      +	git format-patch --always --stdout empty-commit^ >empty-commit.patch &&
      +
       	# reset time
     @@ t/t4150-am.sh: test_expect_success 'apply binary blob in partial clone' '
      +
      +	git am --empty-commit=skip cover-letter.patch >err &&
      +	test_path_is_missing .git/rebase-apply &&
     -+	git rev-parse empty-commit^ >expected &&
     -+	git rev-parse HEAD >actual &&
     -+	test_cmp expected actual
     ++	test_cmp_rev empty-commit^ HEAD
      +'
      +
      +test_expect_success 'record as an empty commit when meeting e-mail message that lacks a patch' '
      +	git am --empty-commit=asis empty-commit.patch &&
      +	test_path_is_missing .git/rebase-apply &&
     -+	git show empty-commit --format="%B" >expected &&
     ++	{
     ++		git show empty-commit --format="%B" &&
     ++		echo "--" &&
     ++		git version | sed -e "s/^git version //" &&
     ++		echo
     ++	} >expected &&
      +	git show HEAD --format="%B" >actual &&
     -+	grep -f actual expected &&
     ++	test_cmp actual expected &&
      +
      +	git am --empty-commit=asis cover-letter.patch &&
      +	test_path_is_missing .git/rebase-apply &&
     -+	git show empty-commit --format="%B" >expected &&
     ++	{
     ++		echo "*** SUBJECT HERE ***" &&
     ++		echo &&
     ++		echo "*** BLURB HERE ***" &&
     ++		echo &&
     ++		echo "A U Thor (1):" &&
     ++		printf "  " &&
     ++		git show empty-commit --format="%B" &&
     ++		echo "--" &&
     ++		git version | sed -e "s/^git version //" &&
     ++		echo
     ++	} >expected &&
      +	git show HEAD --format="%B" >actual &&
     -+	grep -f actual expected
     ++	test_cmp actual expected
      +'
      +
       test_done

-- 
gitgitgadget

From: Aleen <redacted>

Signed-off-by: Aleen <redacted>
---
 Documentation/git-format-patch.txt | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
index 113eabc107c..be797d7a28f 100644
--- a/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt

@@ -18,7 +18,7 @@ SYNOPSIS
 		   [-n | --numbered | -N | --no-numbered]
 		   [--start-number <n>] [--numbered-files]
 		   [--in-reply-to=<message id>] [--suffix=.<sfx>]
-		   [--ignore-if-in-upstream]
+		   [--ignore-if-in-upstream] [--always]
 		   [--cover-from-description=<mode>]
 		   [--rfc] [--subject-prefix=<subject prefix>]
 		   [(--reroll-count|-v) <n>]

@@ -192,6 +192,10 @@ will want to ensure that threading is disabled for `git send-email`.
 	patches being generated, and any patch that matches is
 	ignored.
 
+--always::
+	Include patches for commits that do not introduce any change,
+	which are omitted by default.
+
 --cover-from-description=<mode>::
 	Controls which parts of the cover letter will be automatically
 	populated using the branch's description.

-- 
gitgitgadget

From: Aleen <redacted>

Signed-off-by: Aleen <redacted>
---
 Documentation/git-am.txt |  9 +++++
 builtin/am.c             | 48 +++++++++++++++++++++++---
 t/t4150-am.sh            | 73 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 125 insertions(+), 5 deletions(-)

diff --git a/Documentation/git-am.txt b/Documentation/git-am.txt
index 0a4a984dfde..d8d3bf202d7 100644
--- a/Documentation/git-am.txt
+++ b/Documentation/git-am.txt

@@ -16,6 +16,7 @@ SYNOPSIS
 	 [--exclude=<path>] [--include=<path>] [--reject] [-q | --quiet]
 	 [--[no-]scissors] [-S[<keyid>]] [--patch-format=<format>]
 	 [--quoted-cr=<action>]
+	 [--empty-commit=(die|skip|asis)]
 	 [(<mbox> | <Maildir>)...]
 'git am' (--continue | --skip | --abort | --quit | --show-current-patch[=(diff|raw)])
 

@@ -63,6 +64,14 @@ OPTIONS
 --quoted-cr=<action>::
 	This flag will be passed down to 'git mailinfo' (see linkgit:git-mailinfo[1]).
 
+--empty-commit=(die|skip|asis)::
+	The command usually errors out when seeing an input e-mail
+	message that lacks a patch. When this option is set to
+	'skip', skip such an e-mail message without outputting error.
+	When this option is set to 'asis', create an empty commit,
+	recording the contents of the e-mail message as its log.
+	'die' is specified by default.
+
 -m::
 --message-id::
 	Pass the `-m` flag to 'git mailinfo' (see linkgit:git-mailinfo[1]),

diff --git a/builtin/am.c b/builtin/am.c
index 8677ea2348a..e7755c1377e 100644
--- a/builtin/am.c
+++ b/builtin/am.c

@@ -87,6 +87,12 @@ enum show_patch_type {
 	SHOW_PATCH_DIFF = 1,
 };
 
+enum empty_commit_action {
+	DIE_EMPTY_COMMIT = 0,  /* output errors */
+	SKIP_EMPTY_COMMIT,     /* skip without outputting errors */
+	ASIS_EMPTY_COMMIT      /* keep recording as empty commits */
+};
+
 struct am_state {
 	/* state directory path */
 	char *dir;

@@ -118,6 +124,7 @@ struct am_state {
 	int message_id;
 	int scissors; /* enum scissors_type */
 	int quoted_cr; /* enum quoted_cr_action */
+	int empty_commit; /* enum empty_commit_action */
 	struct strvec git_apply_opts;
 	const char *resolvemsg;
 	int committer_date_is_author_date;

@@ -178,6 +185,23 @@ static int am_option_parse_quoted_cr(const struct option *opt,
 	return 0;
 }
 
+static int am_option_parse_empty_commit(const struct option *opt,
+				     const char *arg, int unset)
+{
+	int *opt_value = opt->value;
+
+	if (unset || !strcmp(arg, "die"))
+		*opt_value = DIE_EMPTY_COMMIT;
+	else if (!strcmp(arg, "skip"))
+		*opt_value = SKIP_EMPTY_COMMIT;
+	else if (!strcmp(arg, "asis"))
+		*opt_value = ASIS_EMPTY_COMMIT;
+	else
+		return error(_("Invalid value for --empty-commit: %s"), arg);
+
+	return 0;
+}
+
 /**
  * Returns path relative to the am_state directory.
  */

@@ -1248,11 +1272,6 @@ static int parse_mail(struct am_state *state, const char *mail)
 		goto finish;
 	}
 
-	if (is_empty_or_missing_file(am_path(state, "patch"))) {
-		printf_ln(_("Patch is empty."));
-		die_user_resolve(state);
-	}
-
 	strbuf_addstr(&msg, "\n\n");
 	strbuf_addbuf(&msg, &mi.log_message);
 	strbuf_stripspace(&msg, 0);

@@ -1792,6 +1811,20 @@ static void am_run(struct am_state *state, int resume)
 		if (state->interactive && do_interactive(state))
 			goto next;
 
+		if (is_empty_or_missing_file(am_path(state, "patch"))) {
+			if (state->empty_commit == SKIP_EMPTY_COMMIT)
+				goto next;
+			else if (state->empty_commit == ASIS_EMPTY_COMMIT) {
+				if (run_applypatch_msg_hook(state))
+					exit(1);
+				else
+					goto commit;
+			} else if (state->empty_commit == DIE_EMPTY_COMMIT) {
+				printf_ln(_("Patch is empty."));
+				die_user_resolve(state);
+			}
+		}
+
 		if (run_applypatch_msg_hook(state))
 			exit(1);
 

@@ -1827,6 +1860,7 @@ static void am_run(struct am_state *state, int resume)
 			die_user_resolve(state);
 		}
 
+commit:
 		do_commit(state);
 
 next:

@@ -2357,6 +2391,10 @@ int cmd_am(int argc, const char **argv, const char *prefix)
 		{ OPTION_STRING, 'S', "gpg-sign", &state.sign_commit, N_("key-id"),
 		  N_("GPG-sign commits"),
 		  PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
+		{ OPTION_CALLBACK, 0, "empty-commit", &state.empty_commit,
+		  "(die|skip|asis)",
+		  N_("specify how to handle empty patches"),
+		  PARSE_OPT_OPTARG, am_option_parse_empty_commit },
 		OPT_HIDDEN_BOOL(0, "rebasing", &state.rebasing,
 			N_("(internal use for git-rebase)")),
 		OPT_END()

diff --git a/t/t4150-am.sh b/t/t4150-am.sh
index 2aaaa0d7ded..e657180c201 100755
--- a/t/t4150-am.sh
+++ b/t/t4150-am.sh

@@ -196,6 +196,13 @@ test_expect_success setup '
 
 	git format-patch -M --stdout lorem^ >rename-add.patch &&
 
+	git checkout -b empty-commit &&
+	git commit -m "empty commit" --allow-empty &&
+
+	git format-patch --stdout empty-commit^ >empty.patch &&
+	git format-patch --stdout --cover-letter empty-commit^ >cover-letter.patch &&
+	git format-patch --always --stdout empty-commit^ >empty-commit.patch &&
+
 	# reset time
 	sane_unset test_tick &&
 	test_tick

@@ -1152,4 +1159,70 @@ test_expect_success 'apply binary blob in partial clone' '
 	git -C client am ../patch
 '
 
+test_expect_success 'still output error with --empty-commit when meeting empty files' '
+	test_must_fail git am --empty-commit=skip empty.patch 2>actual &&
+	echo Patch format detection failed. >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'error when meeting e-mail message that lacks a patch by default' '
+	git checkout empty-commit^ &&
+	test_must_fail git am empty-commit.patch >err &&
+	test_path_is_dir .git/rebase-apply &&
+	test_i18ngrep "Patch is empty." err &&
+	rm -fr .git/rebase-apply &&
+
+	test_must_fail git am --empty-commit=die empty-commit.patch >err &&
+	test_path_is_dir .git/rebase-apply &&
+	test_i18ngrep "Patch is empty." err &&
+	rm -fr .git/rebase-apply &&
+
+	test_must_fail git am --empty-commit=die cover-letter.patch >err &&
+	test_path_is_dir .git/rebase-apply &&
+	test_i18ngrep "Patch is empty." err &&
+	rm -fr .git/rebase-apply
+'
+
+test_expect_success 'skip without error when meeting e-mail message that lacks a patch' '
+	git am --empty-commit=skip empty-commit.patch >err &&
+	test_path_is_missing .git/rebase-apply &&
+	git rev-parse empty-commit^ >expected &&
+	git rev-parse HEAD >actual &&
+	test_cmp expected actual &&
+
+	git am --empty-commit=skip cover-letter.patch >err &&
+	test_path_is_missing .git/rebase-apply &&
+	test_cmp_rev empty-commit^ HEAD
+'
+
+test_expect_success 'record as an empty commit when meeting e-mail message that lacks a patch' '
+	git am --empty-commit=asis empty-commit.patch &&
+	test_path_is_missing .git/rebase-apply &&
+	{
+		git show empty-commit --format="%B" &&
+		echo "--" &&
+		git version | sed -e "s/^git version //" &&
+		echo
+	} >expected &&
+	git show HEAD --format="%B" >actual &&
+	test_cmp actual expected &&
+
+	git am --empty-commit=asis cover-letter.patch &&
+	test_path_is_missing .git/rebase-apply &&
+	{
+		echo "*** SUBJECT HERE ***" &&
+		echo &&
+		echo "*** BLURB HERE ***" &&
+		echo &&
+		echo "A U Thor (1):" &&
+		printf "  " &&
+		git show empty-commit --format="%B" &&
+		echo "--" &&
+		git version | sed -e "s/^git version //" &&
+		echo
+	} >expected &&
+	git show HEAD --format="%B" >actual &&
+	test_cmp actual expected
+'
+
 test_done

-- 
gitgitgadget

Hi Aleen

Thanks for working on this

On 16/11/2021 05:18, Aleen via GitGitGadget wrote:

This feels sufficiently similar to the case of handling empty commits in 
'git rebase' that it is worth trying to have a similar user interface. 
Otherwise the two commands have two different option names doing more or 
less the same thing. 'git rebase' has --empty=[drop,keep,ask] where drop 
is the default. If am were to accept --empty=[drop,keep,die] it would 
offer a similar user experience.

Best Wishes

Phillip

quoted

+--empty-commit=(die|skip|asis)::
+	The command usually errors out when seeing an input e-mail
+	message that lacks a patch. When this option is set to
+	'skip', skip such an e-mail message without outputting error.
+	When this option is set to 'asis', create an empty commit,
+	recording the contents of the e-mail message as its log.
+	'die' is specified by default.

This feels sufficiently similar to the case of handling empty commits in 
'git rebase' that it is worth trying to have a similar user interface. 
Otherwise the two commands have two different option names doing more or 
less the same thing. 'git rebase' has --empty=[drop,keep,ask] where drop 
is the default. If am were to accept --empty=[drop,keep,die] it would 
offer a similar user experience.

Best Wishes

Phillip

Dears Phillip,

It seems a good idea. Can Hamano make a decision?

Aleen

Phillip Wood [off-list ref] writes:

quoted

  +--empty-commit=(die|skip|asis)::
+	The command usually errors out when seeing an input e-mail
+	message that lacks a patch. When this option is set to
+	'skip', skip such an e-mail message without outputting error.
+	When this option is set to 'asis', create an empty commit,
+	recording the contents of the e-mail message as its log.
+	'die' is specified by default.

This feels sufficiently similar to the case of handling empty commits
in 'git rebase' that it is worth trying to have a similar user
interface. Otherwise the two commands have two different option names
doing more or less the same thing. 'git rebase' has
--empty=[drop,keep,ask] where drop is the default. If am were to
 accept --empty=[drop,keep,die] it would offer a similar user
experience.

Ah, thanks for noticing.  I like the three words you suggest.  If we
already have a similar option, we definitely should follow suit, and
I think "--empty" would be a better fit than "--empty-commit" in the
context of talking about the _input_ to "am".

Since that git has supported the --always option for the git-format-patch
command to create a patch with an empty commit message, git-am should
support applying and committing with empty patches.

----------------------------------------------------------------------------

Changes since v1:

 1. add a case when not passing the --always option.
 2. rename the --always option to --allow-empty.

----------------------------------------------------------------------------

Changes since v2:

 1. rename the --allow-empty option to --empty-commit.
 2. introduce three different strategies (die|skip|asis) when trying to
    record empty patches as empty commits.

----------------------------------------------------------------------------

Changes since v3:

 1. generate the missed file for test cases.
 2. grep -f cannot be used under Mac OS.

----------------------------------------------------------------------------

Changes since v4:

 1. rename the --empty-commit option to --empty.
 2. rename three different strategies (die|skip|asis) to die, drop and keep
    correspondingly.

----------------------------------------------------------------------------

Aleen (2):
  doc: git-format-patch: describe the option --always
  am: support --empty option to handle empty patches

 Documentation/git-am.txt           |  9 ++++
 Documentation/git-format-patch.txt |  6 ++-
 builtin/am.c                       | 48 ++++++++++++++++++--
 t/t4150-am.sh                      | 73 ++++++++++++++++++++++++++++++
 4 files changed, 130 insertions(+), 6 deletions(-)


base-commit: b550198c73edd4cc058832dcf74b41aeec2adba2
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1076%2Faleen42%2Fnext-v5
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1076/aleen42/next-v5
Pull-Request: https://github.com/gitgitgadget/git/pull/1076

Range-diff vs v4:

 1:  9f1b3dd6d0b = 1:  9f1b3dd6d0b doc: git-format-patch: describe the option --always
 2:  b7e30c9b7ab ! 2:  96d8573dc80 am: support --empty-commit option to handle empty patches
     @@ Metadata
      Author: Aleen [off-list ref]
      
       ## Commit message ##
     -    am: support --empty-commit option to handle empty patches
     +    am: support --empty option to handle empty patches
      
          Signed-off-by: Aleen [off-list ref]
      
     @@ Documentation/git-am.txt: SYNOPSIS
       	 [--exclude=<path>] [--include=<path>] [--reject] [-q | --quiet]
       	 [--[no-]scissors] [-S[<keyid>]] [--patch-format=<format>]
       	 [--quoted-cr=<action>]
     -+	 [--empty-commit=(die|skip|asis)]
     ++	 [--empty=(die|drop|keep)]
       	 [(<mbox> | <Maildir>)...]
       'git am' (--continue | --skip | --abort | --quit | --show-current-patch[=(diff|raw)])
       
     @@ Documentation/git-am.txt: OPTIONS
       --quoted-cr=<action>::
       	This flag will be passed down to 'git mailinfo' (see linkgit:git-mailinfo[1]).
       
     -+--empty-commit=(die|skip|asis)::
     ++--empty-commit=(die|drop|keep)::
      +	The command usually errors out when seeing an input e-mail
      +	message that lacks a patch. When this option is set to
     -+	'skip', skip such an e-mail message without outputting error.
     -+	When this option is set to 'asis', create an empty commit,
     ++	'drop', skip such an e-mail message without outputting error.
     ++	When this option is set to 'keep', create an empty commit,
      +	recording the contents of the e-mail message as its log.
      +	'die' is specified by default.
      +
     @@ builtin/am.c: enum show_patch_type {
       	SHOW_PATCH_DIFF = 1,
       };
       
     -+enum empty_commit_action {
     ++enum empty_action {
      +	DIE_EMPTY_COMMIT = 0,  /* output errors */
     -+	SKIP_EMPTY_COMMIT,     /* skip without outputting errors */
     -+	ASIS_EMPTY_COMMIT      /* keep recording as empty commits */
     ++	DROP_EMPTY_COMMIT,     /* skip without outputting errors */
     ++	KEEP_EMPTY_COMMIT      /* keep recording as empty commits */
      +};
      +
       struct am_state {
     @@ builtin/am.c: struct am_state {
       	int message_id;
       	int scissors; /* enum scissors_type */
       	int quoted_cr; /* enum quoted_cr_action */
     -+	int empty_commit; /* enum empty_commit_action */
     ++	int empty_type; /* enum empty_action */
       	struct strvec git_apply_opts;
       	const char *resolvemsg;
       	int committer_date_is_author_date;
     @@ builtin/am.c: static int am_option_parse_quoted_cr(const struct option *opt,
      +
      +	if (unset || !strcmp(arg, "die"))
      +		*opt_value = DIE_EMPTY_COMMIT;
     -+	else if (!strcmp(arg, "skip"))
     -+		*opt_value = SKIP_EMPTY_COMMIT;
     -+	else if (!strcmp(arg, "asis"))
     -+		*opt_value = ASIS_EMPTY_COMMIT;
     ++	else if (!strcmp(arg, "drop"))
     ++		*opt_value = DROP_EMPTY_COMMIT;
     ++	else if (!strcmp(arg, "keep"))
     ++		*opt_value = KEEP_EMPTY_COMMIT;
      +	else
     -+		return error(_("Invalid value for --empty-commit: %s"), arg);
     ++		return error(_("Invalid value for --empty: %s"), arg);
      +
      +	return 0;
      +}
     @@ builtin/am.c: static void am_run(struct am_state *state, int resume)
       			goto next;
       
      +		if (is_empty_or_missing_file(am_path(state, "patch"))) {
     -+			if (state->empty_commit == SKIP_EMPTY_COMMIT)
     ++			if (state->empty_type == DROP_EMPTY_COMMIT)
      +				goto next;
     -+			else if (state->empty_commit == ASIS_EMPTY_COMMIT) {
     ++			else if (state->empty_type == KEEP_EMPTY_COMMIT) {
      +				if (run_applypatch_msg_hook(state))
      +					exit(1);
      +				else
      +					goto commit;
     -+			} else if (state->empty_commit == DIE_EMPTY_COMMIT) {
     ++			} else if (state->empty_type == DIE_EMPTY_COMMIT) {
      +				printf_ln(_("Patch is empty."));
      +				die_user_resolve(state);
      +			}
     @@ builtin/am.c: int cmd_am(int argc, const char **argv, const char *prefix)
       		{ OPTION_STRING, 'S', "gpg-sign", &state.sign_commit, N_("key-id"),
       		  N_("GPG-sign commits"),
       		  PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
     -+		{ OPTION_CALLBACK, 0, "empty-commit", &state.empty_commit,
     -+		  "(die|skip|asis)",
     ++		{ OPTION_CALLBACK, 0, "empty", &state.empty_type,
     ++		  "(die|drop|keep)",
      +		  N_("specify how to handle empty patches"),
      +		  PARSE_OPT_OPTARG, am_option_parse_empty_commit },
       		OPT_HIDDEN_BOOL(0, "rebasing", &state.rebasing,
     @@ t/t4150-am.sh: test_expect_success 'apply binary blob in partial clone' '
       	git -C client am ../patch
       '
       
     -+test_expect_success 'still output error with --empty-commit when meeting empty files' '
     -+	test_must_fail git am --empty-commit=skip empty.patch 2>actual &&
     ++test_expect_success 'still output error with --empty when meeting empty files' '
     ++	test_must_fail git am --empty=drop empty.patch 2>actual &&
      +	echo Patch format detection failed. >expected &&
      +	test_cmp expected actual
      +'
     @@ t/t4150-am.sh: test_expect_success 'apply binary blob in partial clone' '
      +	test_i18ngrep "Patch is empty." err &&
      +	rm -fr .git/rebase-apply &&
      +
     -+	test_must_fail git am --empty-commit=die empty-commit.patch >err &&
     ++	test_must_fail git am --empty=die empty-commit.patch >err &&
      +	test_path_is_dir .git/rebase-apply &&
      +	test_i18ngrep "Patch is empty." err &&
      +	rm -fr .git/rebase-apply &&
      +
     -+	test_must_fail git am --empty-commit=die cover-letter.patch >err &&
     ++	test_must_fail git am --empty=die cover-letter.patch >err &&
      +	test_path_is_dir .git/rebase-apply &&
      +	test_i18ngrep "Patch is empty." err &&
      +	rm -fr .git/rebase-apply
      +'
      +
      +test_expect_success 'skip without error when meeting e-mail message that lacks a patch' '
     -+	git am --empty-commit=skip empty-commit.patch >err &&
     ++	git am --empty=drop empty-commit.patch >err &&
      +	test_path_is_missing .git/rebase-apply &&
      +	git rev-parse empty-commit^ >expected &&
      +	git rev-parse HEAD >actual &&
      +	test_cmp expected actual &&
      +
     -+	git am --empty-commit=skip cover-letter.patch >err &&
     ++	git am --empty=drop cover-letter.patch >err &&
      +	test_path_is_missing .git/rebase-apply &&
      +	test_cmp_rev empty-commit^ HEAD
      +'
      +
      +test_expect_success 'record as an empty commit when meeting e-mail message that lacks a patch' '
     -+	git am --empty-commit=asis empty-commit.patch &&
     ++	git am --empty=keep empty-commit.patch &&
      +	test_path_is_missing .git/rebase-apply &&
      +	{
      +		git show empty-commit --format="%B" &&
     @@ t/t4150-am.sh: test_expect_success 'apply binary blob in partial clone' '
      +	git show HEAD --format="%B" >actual &&
      +	test_cmp actual expected &&
      +
     -+	git am --empty-commit=asis cover-letter.patch &&
     ++	git am --empty=keep cover-letter.patch &&
      +	test_path_is_missing .git/rebase-apply &&
      +	{
      +		echo "*** SUBJECT HERE ***" &&

-- 
gitgitgadget

From: Aleen <redacted>

Signed-off-by: Aleen <redacted>
---
 Documentation/git-format-patch.txt | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
index 113eabc107c..be797d7a28f 100644
--- a/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt

@@ -18,7 +18,7 @@ SYNOPSIS
 		   [-n | --numbered | -N | --no-numbered]
 		   [--start-number <n>] [--numbered-files]
 		   [--in-reply-to=<message id>] [--suffix=.<sfx>]
-		   [--ignore-if-in-upstream]
+		   [--ignore-if-in-upstream] [--always]
 		   [--cover-from-description=<mode>]
 		   [--rfc] [--subject-prefix=<subject prefix>]
 		   [(--reroll-count|-v) <n>]

@@ -192,6 +192,10 @@ will want to ensure that threading is disabled for `git send-email`.
 	patches being generated, and any patch that matches is
 	ignored.
 
+--always::
+	Include patches for commits that do not introduce any change,
+	which are omitted by default.
+
 --cover-from-description=<mode>::
 	Controls which parts of the cover letter will be automatically
 	populated using the branch's description.

-- 
gitgitgadget

From: Aleen <redacted>

Signed-off-by: Aleen <redacted>
---
 Documentation/git-am.txt |  9 +++++
 builtin/am.c             | 48 +++++++++++++++++++++++---
 t/t4150-am.sh            | 73 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 125 insertions(+), 5 deletions(-)

diff --git a/Documentation/git-am.txt b/Documentation/git-am.txt
index 0a4a984dfde..665bc89ca9f 100644
--- a/Documentation/git-am.txt
+++ b/Documentation/git-am.txt

@@ -16,6 +16,7 @@ SYNOPSIS
 	 [--exclude=<path>] [--include=<path>] [--reject] [-q | --quiet]
 	 [--[no-]scissors] [-S[<keyid>]] [--patch-format=<format>]
 	 [--quoted-cr=<action>]
+	 [--empty=(die|drop|keep)]
 	 [(<mbox> | <Maildir>)...]
 'git am' (--continue | --skip | --abort | --quit | --show-current-patch[=(diff|raw)])
 

@@ -63,6 +64,14 @@ OPTIONS
 --quoted-cr=<action>::
 	This flag will be passed down to 'git mailinfo' (see linkgit:git-mailinfo[1]).
 
+--empty-commit=(die|drop|keep)::
+	The command usually errors out when seeing an input e-mail
+	message that lacks a patch. When this option is set to
+	'drop', skip such an e-mail message without outputting error.
+	When this option is set to 'keep', create an empty commit,
+	recording the contents of the e-mail message as its log.
+	'die' is specified by default.
+
 -m::
 --message-id::
 	Pass the `-m` flag to 'git mailinfo' (see linkgit:git-mailinfo[1]),

diff --git a/builtin/am.c b/builtin/am.c
index 8677ea2348a..1a3ed87b445 100644
--- a/builtin/am.c
+++ b/builtin/am.c

@@ -87,6 +87,12 @@ enum show_patch_type {
 	SHOW_PATCH_DIFF = 1,
 };
 
+enum empty_action {
+	DIE_EMPTY_COMMIT = 0,  /* output errors */
+	DROP_EMPTY_COMMIT,     /* skip without outputting errors */
+	KEEP_EMPTY_COMMIT      /* keep recording as empty commits */
+};
+
 struct am_state {
 	/* state directory path */
 	char *dir;

@@ -118,6 +124,7 @@ struct am_state {
 	int message_id;
 	int scissors; /* enum scissors_type */
 	int quoted_cr; /* enum quoted_cr_action */
+	int empty_type; /* enum empty_action */
 	struct strvec git_apply_opts;
 	const char *resolvemsg;
 	int committer_date_is_author_date;

@@ -178,6 +185,23 @@ static int am_option_parse_quoted_cr(const struct option *opt,
 	return 0;
 }
 
+static int am_option_parse_empty_commit(const struct option *opt,
+				     const char *arg, int unset)
+{
+	int *opt_value = opt->value;
+
+	if (unset || !strcmp(arg, "die"))
+		*opt_value = DIE_EMPTY_COMMIT;
+	else if (!strcmp(arg, "drop"))
+		*opt_value = DROP_EMPTY_COMMIT;
+	else if (!strcmp(arg, "keep"))
+		*opt_value = KEEP_EMPTY_COMMIT;
+	else
+		return error(_("Invalid value for --empty: %s"), arg);
+
+	return 0;
+}
+
 /**
  * Returns path relative to the am_state directory.
  */

@@ -1248,11 +1272,6 @@ static int parse_mail(struct am_state *state, const char *mail)
 		goto finish;
 	}
 
-	if (is_empty_or_missing_file(am_path(state, "patch"))) {
-		printf_ln(_("Patch is empty."));
-		die_user_resolve(state);
-	}
-
 	strbuf_addstr(&msg, "\n\n");
 	strbuf_addbuf(&msg, &mi.log_message);
 	strbuf_stripspace(&msg, 0);

@@ -1792,6 +1811,20 @@ static void am_run(struct am_state *state, int resume)
 		if (state->interactive && do_interactive(state))
 			goto next;
 
+		if (is_empty_or_missing_file(am_path(state, "patch"))) {
+			if (state->empty_type == DROP_EMPTY_COMMIT)
+				goto next;
+			else if (state->empty_type == KEEP_EMPTY_COMMIT) {
+				if (run_applypatch_msg_hook(state))
+					exit(1);
+				else
+					goto commit;
+			} else if (state->empty_type == DIE_EMPTY_COMMIT) {
+				printf_ln(_("Patch is empty."));
+				die_user_resolve(state);
+			}
+		}
+
 		if (run_applypatch_msg_hook(state))
 			exit(1);
 

@@ -1827,6 +1860,7 @@ static void am_run(struct am_state *state, int resume)
 			die_user_resolve(state);
 		}
 
+commit:
 		do_commit(state);
 
 next:

@@ -2357,6 +2391,10 @@ int cmd_am(int argc, const char **argv, const char *prefix)
 		{ OPTION_STRING, 'S', "gpg-sign", &state.sign_commit, N_("key-id"),
 		  N_("GPG-sign commits"),
 		  PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
+		{ OPTION_CALLBACK, 0, "empty", &state.empty_type,
+		  "(die|drop|keep)",
+		  N_("specify how to handle empty patches"),
+		  PARSE_OPT_OPTARG, am_option_parse_empty_commit },
 		OPT_HIDDEN_BOOL(0, "rebasing", &state.rebasing,
 			N_("(internal use for git-rebase)")),
 		OPT_END()

diff --git a/t/t4150-am.sh b/t/t4150-am.sh
index 2aaaa0d7ded..3119556884d 100755
--- a/t/t4150-am.sh
+++ b/t/t4150-am.sh

@@ -196,6 +196,13 @@ test_expect_success setup '
 
 	git format-patch -M --stdout lorem^ >rename-add.patch &&
 
+	git checkout -b empty-commit &&
+	git commit -m "empty commit" --allow-empty &&
+
+	git format-patch --stdout empty-commit^ >empty.patch &&
+	git format-patch --stdout --cover-letter empty-commit^ >cover-letter.patch &&
+	git format-patch --always --stdout empty-commit^ >empty-commit.patch &&
+
 	# reset time
 	sane_unset test_tick &&
 	test_tick

@@ -1152,4 +1159,70 @@ test_expect_success 'apply binary blob in partial clone' '
 	git -C client am ../patch
 '
 
+test_expect_success 'still output error with --empty when meeting empty files' '
+	test_must_fail git am --empty=drop empty.patch 2>actual &&
+	echo Patch format detection failed. >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'error when meeting e-mail message that lacks a patch by default' '
+	git checkout empty-commit^ &&
+	test_must_fail git am empty-commit.patch >err &&
+	test_path_is_dir .git/rebase-apply &&
+	test_i18ngrep "Patch is empty." err &&
+	rm -fr .git/rebase-apply &&
+
+	test_must_fail git am --empty=die empty-commit.patch >err &&
+	test_path_is_dir .git/rebase-apply &&
+	test_i18ngrep "Patch is empty." err &&
+	rm -fr .git/rebase-apply &&
+
+	test_must_fail git am --empty=die cover-letter.patch >err &&
+	test_path_is_dir .git/rebase-apply &&
+	test_i18ngrep "Patch is empty." err &&
+	rm -fr .git/rebase-apply
+'
+
+test_expect_success 'skip without error when meeting e-mail message that lacks a patch' '
+	git am --empty=drop empty-commit.patch >err &&
+	test_path_is_missing .git/rebase-apply &&
+	git rev-parse empty-commit^ >expected &&
+	git rev-parse HEAD >actual &&
+	test_cmp expected actual &&
+
+	git am --empty=drop cover-letter.patch >err &&
+	test_path_is_missing .git/rebase-apply &&
+	test_cmp_rev empty-commit^ HEAD
+'
+
+test_expect_success 'record as an empty commit when meeting e-mail message that lacks a patch' '
+	git am --empty=keep empty-commit.patch &&
+	test_path_is_missing .git/rebase-apply &&
+	{
+		git show empty-commit --format="%B" &&
+		echo "--" &&
+		git version | sed -e "s/^git version //" &&
+		echo
+	} >expected &&
+	git show HEAD --format="%B" >actual &&
+	test_cmp actual expected &&
+
+	git am --empty=keep cover-letter.patch &&
+	test_path_is_missing .git/rebase-apply &&
+	{
+		echo "*** SUBJECT HERE ***" &&
+		echo &&
+		echo "*** BLURB HERE ***" &&
+		echo &&
+		echo "A U Thor (1):" &&
+		printf "  " &&
+		git show empty-commit --format="%B" &&
+		echo "--" &&
+		git version | sed -e "s/^git version //" &&
+		echo
+	} >expected &&
+	git show HEAD --format="%B" >actual &&
+	test_cmp actual expected
+'
+
 test_done

-- 
gitgitgadget

From: Aleen <redacted>

Signed-off-by: Aleen <redacted>
---
 Documentation/git-format-patch.txt | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
index 113eabc107c..be797d7a28f 100644
--- a/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt

@@ -18,7 +18,7 @@ SYNOPSIS
 		   [-n | --numbered | -N | --no-numbered]
 		   [--start-number <n>] [--numbered-files]
 		   [--in-reply-to=<message id>] [--suffix=.<sfx>]
-		   [--ignore-if-in-upstream]
+		   [--ignore-if-in-upstream] [--always]
 		   [--cover-from-description=<mode>]
 		   [--rfc] [--subject-prefix=<subject prefix>]
 		   [(--reroll-count|-v) <n>]

@@ -192,6 +192,10 @@ will want to ensure that threading is disabled for `git send-email`.
 	patches being generated, and any patch that matches is
 	ignored.
 
+--always::
+	Include patches for commits that do not introduce any change,
+	which are omitted by default.
+
 --cover-from-description=<mode>::
 	Controls which parts of the cover letter will be automatically
 	populated using the branch's description.

-- 
gitgitgadget

Since that git has supported the --always option for the git-format-patch
command to create a patch with an empty commit message, git-am should
support applying and committing with empty patches.

----------------------------------------------------------------------------

Changes since v1:

 1. add a case when not passing the --always option.
 2. rename the --always option to --allow-empty.

----------------------------------------------------------------------------

Changes since v2:

 1. rename the --allow-empty option to --empty-commit.
 2. introduce three different strategies (die|skip|asis) when trying to
    record empty patches as empty commits.

----------------------------------------------------------------------------

Changes since v3:

 1. generate the missed file for test cases.
 2. grep -f cannot be used under Mac OS.

----------------------------------------------------------------------------

Changes since v4:

 1. rename the --empty-commit option to --empty.
 2. rename three different strategies (die|skip|asis) to die, drop and keep
    correspondingly.

----------------------------------------------------------------------------

Changes since v5:

 1. throw an error when passing --empty option without value.

----------------------------------------------------------------------------

Aleen (3):
  doc: git-format-patch: describe the option --always
  am: support --empty option to handle empty patches
  am: throw an error when passing --empty option without value

 Documentation/git-am.txt           |  9 ++++
 Documentation/git-format-patch.txt |  6 ++-
 builtin/am.c                       | 49 ++++++++++++++++--
 t/t4150-am.sh                      | 79 ++++++++++++++++++++++++++++++
 4 files changed, 137 insertions(+), 6 deletions(-)


base-commit: b550198c73edd4cc058832dcf74b41aeec2adba2
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1076%2Faleen42%2Fnext-v6
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1076/aleen42/next-v6
Pull-Request: https://github.com/gitgitgadget/git/pull/1076

Range-diff vs v5:

 1:  9f1b3dd6d0b = 1:  9f1b3dd6d0b doc: git-format-patch: describe the option --always
 2:  96d8573dc80 = 2:  96d8573dc80 am: support --empty option to handle empty patches
 -:  ----------- > 3:  e907a2b2faa am: throw an error when passing --empty option without value

-- 
gitgitgadget

From: Aleen <redacted>

Signed-off-by: Aleen <redacted>
---
 Documentation/git-am.txt |  9 +++++
 builtin/am.c             | 48 +++++++++++++++++++++++---
 t/t4150-am.sh            | 73 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 125 insertions(+), 5 deletions(-)

diff --git a/Documentation/git-am.txt b/Documentation/git-am.txt
index 0a4a984dfde..665bc89ca9f 100644
--- a/Documentation/git-am.txt
+++ b/Documentation/git-am.txt

@@ -16,6 +16,7 @@ SYNOPSIS
 	 [--exclude=<path>] [--include=<path>] [--reject] [-q | --quiet]
 	 [--[no-]scissors] [-S[<keyid>]] [--patch-format=<format>]
 	 [--quoted-cr=<action>]
+	 [--empty=(die|drop|keep)]
 	 [(<mbox> | <Maildir>)...]
 'git am' (--continue | --skip | --abort | --quit | --show-current-patch[=(diff|raw)])
 

@@ -63,6 +64,14 @@ OPTIONS
 --quoted-cr=<action>::
 	This flag will be passed down to 'git mailinfo' (see linkgit:git-mailinfo[1]).
 
+--empty-commit=(die|drop|keep)::
+	The command usually errors out when seeing an input e-mail
+	message that lacks a patch. When this option is set to
+	'drop', skip such an e-mail message without outputting error.
+	When this option is set to 'keep', create an empty commit,
+	recording the contents of the e-mail message as its log.
+	'die' is specified by default.
+
 -m::
 --message-id::
 	Pass the `-m` flag to 'git mailinfo' (see linkgit:git-mailinfo[1]),

diff --git a/builtin/am.c b/builtin/am.c
index 8677ea2348a..1a3ed87b445 100644
--- a/builtin/am.c
+++ b/builtin/am.c

@@ -87,6 +87,12 @@ enum show_patch_type {
 	SHOW_PATCH_DIFF = 1,
 };
 
+enum empty_action {
+	DIE_EMPTY_COMMIT = 0,  /* output errors */
+	DROP_EMPTY_COMMIT,     /* skip without outputting errors */
+	KEEP_EMPTY_COMMIT      /* keep recording as empty commits */
+};
+
 struct am_state {
 	/* state directory path */
 	char *dir;

@@ -118,6 +124,7 @@ struct am_state {
 	int message_id;
 	int scissors; /* enum scissors_type */
 	int quoted_cr; /* enum quoted_cr_action */
+	int empty_type; /* enum empty_action */
 	struct strvec git_apply_opts;
 	const char *resolvemsg;
 	int committer_date_is_author_date;

@@ -178,6 +185,23 @@ static int am_option_parse_quoted_cr(const struct option *opt,
 	return 0;
 }
 
+static int am_option_parse_empty_commit(const struct option *opt,
+				     const char *arg, int unset)
+{
+	int *opt_value = opt->value;
+
+	if (unset || !strcmp(arg, "die"))
+		*opt_value = DIE_EMPTY_COMMIT;
+	else if (!strcmp(arg, "drop"))
+		*opt_value = DROP_EMPTY_COMMIT;
+	else if (!strcmp(arg, "keep"))
+		*opt_value = KEEP_EMPTY_COMMIT;
+	else
+		return error(_("Invalid value for --empty: %s"), arg);
+
+	return 0;
+}
+
 /**
  * Returns path relative to the am_state directory.
  */