Re: [PATCH v2 02/12] fmt-merge-msg: introduce a way to override the main branch name

Hi Phillip,

On Mon, 15 Jun 2020, Phillip Wood wrote:

On 15/06/2020 13:50, Johannes Schindelin via GitGitGadget wrote:

quoted

From: Johannes Schindelin <redacted>

There is a growing number of projects and companies desiring to change
the main branch name of their repositories (see e.g.
https://twitter.com/mislav/status/1270388510684598272 for background on
this).

I think this is a good way of phrasing the rationale for the change

As I am replacing this patch in v3 with a version that simply drops the
special handling of the `master` branch, I moved that rationale into the
patch introducing support for `git init --initial-branch=<name>`.

quoted

However, there are a couple of hard-coded spots in Git's source code
that make this endeavor harder than necessary. For example, when
formatting the commit message for merge commits, Git appends "into
<branch-name>" unless the current branch is the `master` branch.

Clearly, this is not what one wants when already having gone through all
the steps to manually rename the main branch

This didn't quite scan for me maybe s/already having/one has already/ ?

Thank you! If I had not dropped that part of the commit message, I would
have taken your suggested fix.

quoted

(and taking care of all the
fall-out such as re-targeting existing Pull Requests).

Let's introduce a way to override Git's hard-coded default:
`core.mainBranch`.

We will start supporting this config option in the `git fmt-merge-msg`
command and successively adjust all other places where the main branch
name is hard-coded.

Signed-off-by: Johannes Schindelin <redacted>
---
  Documentation/config/core.txt |  5 +++++
  fmt-merge-msg.c               |  6 ++++--
  refs.c                        | 27 +++++++++++++++++++++++++++
  refs.h                        |  7 +++++++
  t/t6200-fmt-merge-msg.sh      |  7 +++++++
  5 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/Documentation/config/core.txt b/Documentation/config/core.txt
index 74619a9c03b..32bb5368ebb 100644
--- a/Documentation/config/core.txt
+++ b/Documentation/config/core.txt

@@ -626,3 +626,8 @@ core.abbrev::
   in your repository, which hopefully is enough for
   abbreviated object names to stay unique for some time.
   The minimum length is 4.
+
+core.mainBranch::
+	The name of the main (or: primary) branch in the current repository.
+	For historical reasons, `master` is used as the fall-back for this
+	setting.

diff --git a/fmt-merge-msg.c b/fmt-merge-msg.c
index 72d32bd73b1..43f4f829242 100644
--- a/fmt-merge-msg.c
+++ b/fmt-merge-msg.c

@@ -407,7 +407,7 @@ static void fmt_merge_msg_title(struct strbuf *out,
  				const char *current_branch)
  {
  	int i = 0;
-	char *sep = "";
+	char *sep = "", *main_branch;

   strbuf_addstr(out, "Merge ");
   for (i = 0; i < srcs.nr; i++) {

@@ -451,10 +451,12 @@ static void fmt_merge_msg_title(struct strbuf *out,
   		strbuf_addf(out, " of %s", srcs.items[i].string);
   }
  -	if (!strcmp("master", current_branch))
+	main_branch = git_main_branch_name();
+	if (!strcmp(main_branch, current_branch))
   	strbuf_addch(out, '\n');
   else
  		strbuf_addf(out, " into %s\n", current_branch);
+	free(main_branch);
  }

  static void fmt_tag_signature(struct strbuf *tagbuf,

diff --git a/refs.c b/refs.c
index 224ff66c7bb..f1854cffa2f 100644
--- a/refs.c
+++ b/refs.c

@@ -560,6 +560,33 @@ void expand_ref_prefix(struct argv_array *prefixes,

const char *prefix)
  		argv_array_pushf(prefixes, *p, len, prefix);
  }

+char *repo_main_branch_name(struct repository *r)
+{
+	const char *config_key = "core.mainbranch";
+	const char *config_display_key = "core.mainBranch";
+	const char *fall_back = "master";
+	char *name = NULL, *ret;
+
+	if (repo_config_get_string(r, config_key, &name) < 0)
+		die(_("could not retrieve `%s`"), config_display_key);
+
+	ret = name ? name : xstrdup(fall_back);
+
+	if (check_refname_format(ret, REFNAME_ALLOW_ONELEVEL))
+		die(_("invalid branch name: %s = %s"),
+		    config_display_key, name);
+
+	if (name != ret)
+		free(name);

I'm struggling to come up with a scenario where name != NULL && name != ret
here, however once we get to patch 4 that scenario definitely does exist.

Right.

But as I am dropping the concept of `core.mainBranch` from v3, this won't
apply anymore.

quoted

+
+	return ret;
+}
+
+char *git_main_branch_name(void)
+{
+	return repo_main_branch_name(the_repository);
+}
+
  /*
   * *string and *len will only be substituted, and *string returned (for
   * later free()ing) if the string passed in is a magic short-hand form

diff --git a/refs.h b/refs.h
index a92d2c74c83..a207ef01348 100644
--- a/refs.h
+++ b/refs.h

@@ -154,6 +154,13 @@ int repo_dwim_log(struct repository *r, const char

*str, int len, struct object_
  int dwim_ref(const char *str, int len, struct object_id *oid, char **ref);
  int dwim_log(const char *str, int len, struct object_id *oid, char **ref);

+/*
+ * Retrieves the name of the main (or: primary) branch of the given

nit pick, I'm confused by the ':'

Right, v3 won't have that peculiar construct.

Thank you for your review!
Dscho

Best Wishes

Phillip

quoted

+ * repository.
+ */
+char *git_main_branch_name(void);
+char *repo_main_branch_name(struct repository *r);
+
  /*
   * A ref_transaction represents a collection of reference updates that
   * should succeed or fail together.

diff --git a/t/t6200-fmt-merge-msg.sh b/t/t6200-fmt-merge-msg.sh
index e4c2a6eca43..7a873f4a05c 100755
--- a/t/t6200-fmt-merge-msg.sh
+++ b/t/t6200-fmt-merge-msg.sh

@@ -158,6 +158,13 @@ test_expect_success 'setup FETCH_HEAD' '
  	git fetch . left
  '

+test_expect_success 'with overridden default branch name' '
+	test_when_finished "git switch master" &&
+	git switch -c default &&
+	git -c core.mainBranch=default fmt-merge-msg <.git/FETCH_HEAD >actual

&&
+	! grep "into default" actual
+'
+
  test_expect_success 'merge.log=3 limits shortlog length' '
   cat >expected <<-EOF &&
   Merge branch ${apos}left${apos}