submodule update: allow '.' for branch value

Gerrit has a "superproject subscription" feature[1], that triggers a
commit in a superproject that is subscribed to its submodules.
Conceptually this Gerrit feature can be done on the client side with
Git via (except for raciness, error handling etc):

while [ true ]; do
git -C <superproject> submodule update --remote --force
git -C <superproject> commit -a -m "Update submodules"
git -C <superproject> push
done

for each branch in the superproject. To ease the configuration in Gerrit
a special value of "." has been introduced for the submodule.<name>.branch
to mean the same branch as the superproject[2], such that you can create a
new branch on both superproject and the submodule and this feature
continues to work on that new branch.

Now we find projects in the wild with such a .gitmodules file.
The .gitmodules used in these Gerrit projects do not conform
to Gits understanding of how .gitmodules should look like.
This teaches Git to deal gracefully with this syntax as well.

The redefinition of "." does no harm to existing projects unaware of
this change, as "." is an invalid branch name in Git, so we do not
expect such projects to exist.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index 9be2c75e0e330c45e3d2092f102c0b09c10e7e2c..f1acc4dc96ff45094d48ba9e18afa8d03f8e812e 100644 (file)
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -912,6 +912,24 @@ static const char *remote_submodule_branch(const char *path)
        if (!sub->branch)
                return "master";
 
        if (!sub->branch)
                return "master";
 

+       if (!strcmp(sub->branch, ".")) {
+               unsigned char sha1[20];
+               const char *refname = resolve_ref_unsafe("HEAD", 0, sha1, NULL);
+
+               if (!refname)
+                       die(_("No such ref: %s"), "HEAD");
+
+               /* detached HEAD */
+               if (!strcmp(refname, "HEAD"))
+                       die(_("Submodule (%s) branch configured to inherit "
+                             "branch from superproject, but the superproject "
+                             "is not on any branch"), sub->name);
+
+               if (!skip_prefix(refname, "refs/heads/", &refname))
+                       die(_("Expecting a full ref name, got %s"), refname);
+               return refname;
+       }
+

        return sub->branch;
 }
 
        return sub->branch;
 }
 

diff --git a/t/t7406-submodule-update.sh b/t/t7406-submodule-update.sh
index 1bb1f4382460a8df095a642ed1f048a52ec0e6e0..d7983cf09fc3fe407378745a3bb44281542d7ef4 100755 (executable)
--- a/t/t7406-submodule-update.sh
+++ b/t/t7406-submodule-update.sh
@@ -209,9 +209,42 @@ test_expect_success 'submodule update --remote should fetch upstream changes' '
        )
 '
 
        )
 '
 

+test_expect_success 'submodule update --remote should fetch upstream changes with .' '
+       (
+               cd super &&
+               git config -f .gitmodules submodule."submodule".branch "." &&
+               git add .gitmodules &&
+               git commit -m "submodules: update from the respective superproject branch"
+       ) &&
+       (
+               cd submodule &&
+               echo line4a >> file &&
+               git add file &&
+               test_tick &&
+               git commit -m "upstream line4a" &&
+               git checkout -b test-branch &&
+               test_commit on-test-branch
+       ) &&
+       (
+               cd super &&
+               git submodule update --remote --force submodule &&
+               git -C submodule log -1 --oneline >actual
+               git -C ../submodule log -1 --oneline master >expect
+               test_cmp expect actual &&
+               git checkout -b test-branch &&
+               git submodule update --remote --force submodule &&
+               git -C submodule log -1 --oneline >actual
+               git -C ../submodule log -1 --oneline test-branch >expect
+               test_cmp expect actual &&
+               git checkout master &&
+               git branch -d test-branch &&
+               git reset --hard HEAD^
+       )
+'
+

 test_expect_success 'local config should override .gitmodules branch' '
        (cd submodule &&
 test_expect_success 'local config should override .gitmodules branch' '
        (cd submodule &&

-        git checkout -b test-branch &&
+        git checkout test-branch &&

         echo line5 >> file &&
         git add file &&
         test_tick &&
         echo line5 >> file &&
         git add file &&
         test_tick &&