On Fri, Apr 09, 2021 at 11:35:13AM -0300, Matheus Tavares Bernardino wrote:

Hi, Emily

I'm not familiar enough with this code to give a full review and I
imagine you probably want comments more focused on the design level,
while this is an RFC, but here are some small nitpicks I found while
reading the patch. I Hope it helps :)

On Thu, Apr 8, 2021 at 8:39 PM Emily Shaffer [off-list ref] wrote:

quoted

diff --git a/Documentation/git-config.txt b/Documentation/git-config.txt
index 4b4cc5c5e8..a33136fb08 100644
--- a/Documentation/git-config.txt
+++ b/Documentation/git-config.txt

@@ -48,7 +48,7 @@ unset an existing `--type` specifier with `--no-type`.

 When reading, the values are read from the system, global and
 repository local configuration files by default, and options
-`--system`, `--global`, `--local`, `--worktree` and
+`--system`, `--global`, `--superproject`, `--local`, `--worktree` and
 `--file <filename>` can be used to tell the command to read from only
 that location (see <<FILES>>).

@@ -127,6 +127,17 @@ rather than from all available files.
 +
 See also <<FILES>>.

+--superproject::
+       For writing options: write to the superproject's
+       `.git/config.superproject` file, even if run from a submodule of that
+       superproject.

Hmm, I wonder what happens if a repo is both a submodule and a
superproject (i.e. in case of nested submodules). Let's see:

# Create repo/sub/sub2
$ git init repo
$ cd repo
$ touch F && git add F && git commit -m F
$ git submodule add ./ sub
$ git -C sub submodule add ./sub sub2
$ git -C sub commit -m sub2
$ git commit -m sub

# Now test the config
$ git -C sub/sub2 config --superproject foo.bar 1
$ git -C sub/sub2 config --get foo.bar
1
$ git -C sub config --get foo.bar
<nothing>
$ git config --get foo.bar
<nothing>

It makes sense to me that `foo.bar` is not defined on `repo`, but
shouldn't it be defined on `repo/sub`? Or am I doing something wrong?

(`git -C sub rev-parse --git-dir` gives `.git/modules/sub/`, where
indeed there is a config.superproject with `foo.bar` set.)

Yeah, this isn't very surprising. The code does essentially:

  parent_gitdir = git -C ../ rev-parse --git-dir
  config_parse_order += $parent_gitdir/config.superproject

That is, in the nested submodules case, it's looking at
.git/modules/sub/config.superproject - but 'sub' is getting its
superproject config from .git/config.superproject and has no such file
of its own.

One way I could see to solve it would be to skip the "find parent
gitdir" thing entirely:

  git -C ../ config --superproject --list >parent_superproject_cfg
  config_parse_order += parent_superproject_cfg
  config_parse_order += $my_own_gitdir/config.superproject

The recursion is a little icky, I guess, but submodules are all
recursive anyway, right? :) Hmm.

quoted

diff --git a/builtin/config.c b/builtin/config.c
index f71fa39b38..f0a57a89ca 100644
--- a/builtin/config.c
+++ b/builtin/config.c

@@ -26,7 +26,7 @@ static char key_delim = ' ';
 static char term = '\n';

 static int use_global_config, use_system_config, use_local_config;
-static int use_worktree_config;
+static int use_worktree_config, use_superproject_config;
 static struct git_config_source given_config_source;
 static int actions, type;
 static char *default_value;

@@ -130,6 +130,8 @@ static struct option builtin_config_options[] = {
        OPT_GROUP(N_("Config file location")),
        OPT_BOOL(0, "global", &use_global_config, N_("use global config file")),
        OPT_BOOL(0, "system", &use_system_config, N_("use system config file")),
+       OPT_BOOL(0, "superproject",
+                &use_superproject_config, N_("use superproject config file")),
        OPT_BOOL(0, "local", &use_local_config, N_("use repository config file")),
        OPT_BOOL(0, "worktree", &use_worktree_config, N_("use per-worktree config file")),
        OPT_STRING('f', "file", &given_config_source.file, N_("file"), N_("use given config file")),

@@ -697,6 +699,12 @@ int cmd_config(int argc, const char **argv, const char *prefix)
        else if (use_system_config) {
                given_config_source.file = git_etc_gitconfig();
                given_config_source.scope = CONFIG_SCOPE_SYSTEM;
+       } else if (use_superproject_config) {
+               struct strbuf superproject_cfg = STRBUF_INIT;
+               git_config_superproject(&superproject_cfg, get_git_dir());
+               given_config_source.file = xstrdup(superproject_cfg.buf);
+               given_config_source.scope = CONFIG_SCOPE_SUPERPROJECT;
+               strbuf_release(&superproject_cfg);

Nit: maybe it would be a bit cleaner to replace the xstrdup() +
strbuf_release() lines with a single:

    given_config_source.file = strbuf_detach(superproject_cfg, NULL);

Oh nice, thanks!

quoted

        } else if (use_local_config) {
                given_config_source.file = git_pathdup("config");
                given_config_source.scope = CONFIG_SCOPE_LOCAL;

diff --git a/config.c b/config.c
index 67d9bf2238..28bb80fd0d 100644
--- a/config.c
+++ b/config.c

@@ -21,6 +21,7 @@
 #include "dir.h"
 #include "color.h"
 #include "refs.h"
+#include "submodule.h"

 struct config_source {
        struct config_source *prev;

@@ -1852,6 +1853,17 @@ const char *git_etc_gitconfig(void)
        return system_wide;
 }

+void git_config_superproject(struct strbuf *sb, const char *gitdir)
+{
+       if (!get_superproject_gitdir(sb)) {
+               /* not a submodule */
+               strbuf_reset(sb);

Do we have to reset `sb` here? It seems that get_superproject_gitdir()
leaves the buffer empty when we are not inside a submodule.

Since I didn't promise it in the documentation I included the reset
here, but I see your comment just after this suggesting I should also
promise it in the documentation ;)

quoted

diff --git a/submodule.h b/submodule.h
index 4ac6e31cf1..1308d5ae2d 100644
--- a/submodule.h
+++ b/submodule.h

@@ -149,6 +149,12 @@ void prepare_submodule_repo_env(struct strvec *out);
 void absorb_git_dir_into_superproject(const char *path,
                                      unsigned flags);

+/*
+ * Return the gitdir of the superproject, which this project is a submodule of.
+ * If this repository is not a submodule of another repository, return 0.

Nit: it might be nice to say what's the state of `buf` on a 0 return.
Perhaps also be more explicit about the return codes? Maybe something
like:

"If this repository is a submodule of another repository, save the
superproject's gitdir on `buf` and return 1. Otherwise, return 0 and
leave `buf` empty."

Seems reasonable.

quoted

+int get_superproject_gitdir(struct strbuf *buf);
+
 /*
  * Return the absolute path of the working tree of the superproject, which this
  * project is a submodule of. If this repository is not a submodule of

diff --git a/t/t1311-superproject-config.sh b/t/t1311-superproject-config.sh
new file mode 100755
index 0000000000..650c4d24c7
--- /dev/null
+++ b/t/t1311-superproject-config.sh

@@ -0,0 +1,124 @@

[...]

quoted

+test_expect_success 'superproject config applies to super and submodule' '
+       cat >.git/config.superproject <<-EOF &&
+       [foo]
+               bar = baz
+       EOF
+
+       git config --get foo.bar &&
+       git -C sub config --get foo.bar &&
+
+       rm .git/config.superproject

Hmm, if this test fails before removing the config.superproject file,
couldn't it interfere with other tests (like the 'can --edit
superproject config')? Perhaps this and the other similar cleanup
removals could be declared inside a `test_when_finished` clause, to
ensure they are performed even on test failure.

Oh sure, thanks.

quoted

+test_expect_success 'can --unset from super or sub' '
+       git config --superproject apple.species honeycrisp &&
+       git -C sub config --superproject banana.species cavendish &&
+
+       git config --unset --superproject banana.species &&
+       git -C sub config --unset --superproject apple.species
+'

Nice "cross-setting/unsetting" test :)

[...]

quoted

+# This test deletes the submodule! Keep it at the end of the test suite.
+test_expect_success 'config.submodule works even with no submodules' '

s/config.submodule/config.superproject/ ?

Aaauuurgggh :)

Thanks for the nits!
 - Emily