Re: [RFC PATCH 2/2] config: add 'config.superproject' file

[Matheus Tavares Bernardino <matheus.bernardino@usp.br>]

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 <emilyshaffer@google.com> wrote:
>
> 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.)

> 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);

>         } 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.

> 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."

> +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 @@
[...]
> +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.

> +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 :)

[...]
> +# 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/ ?