Re: [PATCH v2] Submodule: use the submodule repository to abbreviate commits

>
> Hi Srujith,
>
> On Sat, Oct 31, 2026 at 7:57 PM Srujith A Poojary via GitGitGadget
> <gitgitgadget@gmail.com> wrote:
> > + struct repository *repo = sub ? sub : o->repo;
>
> Thanks, v2 looks good to me.
>
> > Submodule: use the submodule repository to abbreviate commits
>
> One small nit: "git log --no-merges submodule.c" shows the area is
> always written in lowercase ("submodule:"), so "submodule: use the
> submodule repository to abbreviate commits" would match.
>
> Thanks,
> Okhuomon
>
> On Sat, Oct 31, 2026 at 7:57 PM Srujith A Poojary via GitGitGadget
> <gitgitgadget@gmail.com> wrote:
> >
> > From: Srujith A Poojary <poojarysrujith@gmail.com>
> >
> > The commit IDs shown in a submodule diff header belong to the
> > submodule's object database. However, strbuf_add_unique_abbrev()
> > uses the_repository, so it checks the superproject's object
> > database when abbreviating those IDs.
> >
> > Use the submodule repository when it is available, and fall back
> > to the repository from the diff options when it is not.
> >
> > Signed-off-by: Srujith A Poojary <poojarysrujith@gmail.com>
> > ---
> >     [Outreachy PATCH] t4041: use submodule repository for commit
> >     abbreviations
> >
> > Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2288%2Fpoojarysrujith%2Fmicroproject-git-libification-v2
> > Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2288/poojarysrujith/microproject-git-libification-v2
> > Pull-Request: https://github.com/gitgitgadget/git/pull/2288
> >
> > Range-diff vs v1:
> >
> >  1:  7b2af1b46a ! 1:  3133cd3017 [Outreachy PATCH] t4041: use submodule repository for commit abbreviations
> >      @@ Metadata
> >       Author: Srujith A Poojary <poojarysrujith@gmail.com>
> >
> >        ## Commit message ##
> >      -    [Outreachy PATCH] t4041: use submodule repository for commit abbreviations
> >      +    Submodule: use the submodule repository to abbreviate commits
> >
> >      -    Use the submodule repository when abbreviating commit IDs in
> >      -    submodule diff headers, so uniqueness is checked against the
> >      -    correct object database.
> >      +    The commit IDs shown in a submodule diff header belong to the
> >      +    submodule's object database. However, strbuf_add_unique_abbrev()
> >      +    uses the_repository, so it checks the superproject's object
> >      +    database when abbreviating those IDs.
> >      +
> >      +    Use the submodule repository when it is available, and fall back
> >      +    to the repository from the diff options when it is not.
> >
> >           Signed-off-by: Srujith A Poojary <poojarysrujith@gmail.com>
> >
> >        ## submodule.c ##
> >       @@ submodule.c: static void show_submodule_header(struct diff_options *o,
> >      +          struct commit **left, struct commit **right,
> >      +          struct commit_list **merge_bases)
> >      + {
> >      ++ struct repository *repo = sub ? sub : o->repo;
> >      +  const char *message = NULL;
> >      +  struct strbuf sb = STRBUF_INIT;
> >      +  int fast_forward = 0, fast_backward = 0;
> >      +@@ submodule.c: static void show_submodule_header(struct diff_options *o,
> >
> >        output_header:
> >         strbuf_addf(&sb, "Submodule %s ", path);
> >       - strbuf_add_unique_abbrev(&sb, one, DEFAULT_ABBREV);
> >      -+ if (sub)
> >      -+         strbuf_repo_add_unique_abbrev(&sb, sub, one, DEFAULT_ABBREV);
> >      -+ else
> >      -+         strbuf_add_unique_abbrev(&sb, one, DEFAULT_ABBREV);
> >      ++ strbuf_repo_add_unique_abbrev(&sb, repo, one, DEFAULT_ABBREV);
> >         strbuf_addstr(&sb, (fast_backward || fast_forward) ? ".." : "...");
> >       - strbuf_add_unique_abbrev(&sb, two, DEFAULT_ABBREV);
> >      -+ if (sub)
> >      -+         strbuf_repo_add_unique_abbrev(&sb, sub, two, DEFAULT_ABBREV);
> >      -+ else
> >      -+         strbuf_add_unique_abbrev(&sb, two, DEFAULT_ABBREV);
> >      ++ strbuf_repo_add_unique_abbrev(&sb, repo, two, DEFAULT_ABBREV);
> >         if (message)
> >                 strbuf_addf(&sb, " %s\n", message);
> >         else
> >
> >
> >  submodule.c                      |  5 +++--
> >  t/t4041-diff-submodule-option.sh | 18 ++++++++++++++++++
> >  2 files changed, 21 insertions(+), 2 deletions(-)
> >
> > diff --git a/submodule.c b/submodule.c
> > index 6fcb606f7e..1302c11ddf 100644
> > --- a/submodule.c
> > +++ b/submodule.c
> > @@ -543,6 +543,7 @@ static void show_submodule_header(struct diff_options *o,
> >                 struct commit **left, struct commit **right,
> >                 struct commit_list **merge_bases)
> >  {
> > +       struct repository *repo = sub ? sub : o->repo;
> >         const char *message = NULL;
> >         struct strbuf sb = STRBUF_INIT;
> >         int fast_forward = 0, fast_backward = 0;
> > @@ -599,9 +600,9 @@ static void show_submodule_header(struct diff_options *o,
> >
> >  output_header:
> >         strbuf_addf(&sb, "Submodule %s ", path);
> > -       strbuf_add_unique_abbrev(&sb, one, DEFAULT_ABBREV);
> > +       strbuf_repo_add_unique_abbrev(&sb, repo, one, DEFAULT_ABBREV);
> >         strbuf_addstr(&sb, (fast_backward || fast_forward) ? ".." : "...");
> > -       strbuf_add_unique_abbrev(&sb, two, DEFAULT_ABBREV);
> > +       strbuf_repo_add_unique_abbrev(&sb, repo, two, DEFAULT_ABBREV);
> >         if (message)
> >                 strbuf_addf(&sb, " %s\n", message);
> >         else
> > diff --git a/t/t4041-diff-submodule-option.sh b/t/t4041-diff-submodule-option.sh
> > index 4dd4954260..e80472af32 100755
> > --- a/t/t4041-diff-submodule-option.sh
> > +++ b/t/t4041-diff-submodule-option.sh
> > @@ -14,6 +14,24 @@ export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
> >
> >  . ./test-lib.sh
> >
> > +test_expect_success SHA1 'submodule commit abbreviation uses submodule object database' '
> > +       test_when_finished "rm -rf collision-super" &&
> > +       git init -q collision-super &&
> > +       git init -q collision-super/sm1 &&
> > +       printf "0\n1\n2\n3\n4\n5\n6\n7\n8\n9\n\nb1rwzyc3\n" >collision-super/sm1/a0blgqsjc &&
> > +       git -C collision-super/sm1 add a0blgqsjc &&
> > +       tree=$(git -C collision-super/sm1 write-tree) &&
> > +       commit1=$(GIT_AUTHOR_DATE="1112911993 -0700" GIT_COMMITTER_DATE="1112911993 -0700" git -C collision-super/sm1 commit-tree "$tree" -m a2onsxbvj) &&
> > +       commit2=$(printf "child\n" | GIT_AUTHOR_DATE="1112912053 -0700" GIT_COMMITTER_DATE="1112912053 -0700" git -C collision-super/sm1 commit-tree "$tree" -p "$commit1") &&
> > +       git -C collision-super/sm1 checkout -q "$commit2" &&
> > +       git -C collision-super update-index --add --cacheinfo 160000,"$commit1",sm1 &&
> > +       git -C collision-super commit -q -m "Add submodule" &&
> > +       git -C collision-super diff --submodule=log >actual &&
> > +       printf "Submodule sm1 0000000000e..%s:\n  > child\n" \
> > +               "$(git -C collision-super/sm1 rev-parse --short "$commit2")" >expected &&
> > +       test_cmp expected actual
> > +'
> > +
> >  # Test non-UTF-8 encoding in case iconv is available.
> >  if test_have_prereq ICONV
> >  then
> >
> > base-commit: 50fe5cc63f9cd6e89b87a2c9ccf96a444f4cfdb7
> > --
> > gitgitgadget