[PATCH 5/6] fetch/pull: Don't recurse into a submodule when commits are already present

[Jens Lehmann <Jens.Lehmann@web.de>]

When looking for submodules where new commits have been recorded in the
superproject ignore those cases where the submodules commits are already
present locally. This can happen e.g. when the submodule has been rewound
to an earlier state. Then there is no need to fetch the submodule again
as the commit recorded in the newly fetched superproject commit has
already been fetched earlier into the submodule.

Signed-off-by: Jens Lehmann <Jens.Lehmann@web.de>
---
 submodule.c                 |    9 ++++++++-
 t/t5526-fetch-submodules.sh |   19 +++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletions(-)

diff --git a/submodule.c b/submodule.c
index b477c3c..ddb0a29 100644
--- a/submodule.c
+++ b/submodule.c
@@ -263,6 +263,13 @@ void set_config_fetch_recurse_submodules(int value)
 	config_fetch_recurse_submodules = value;
 }

+static int is_submodule_commit_present(const char *path, unsigned char sha1[20])
+{
+	if (!add_submodule_odb(path))
+		return lookup_commit_reference(sha1) != 0;
+	return 0;
+}
+
 static void submodule_collect_changed_cb(struct diff_queue_struct *q,
 					 struct diff_options *options,
 					 void *data)
@@ -280,7 +287,7 @@ static void submodule_collect_changed_cb(struct diff_queue_struct *q,
 			 * being moved around. */
 			struct string_list_item *path;
 			path = unsorted_string_list_lookup(&changed_submodule_paths, p->two->path);
-			if (!path)
+			if (!path && !is_submodule_commit_present(p->two->path, p->two->sha1))
 				string_list_append(&changed_submodule_paths, xstrdup(p->two->path));
 		} else {
 			/* Submodule is new or was moved here */
diff --git a/t/t5526-fetch-submodules.sh b/t/t5526-fetch-submodules.sh
index 09701aa..3decfae 100755
--- a/t/t5526-fetch-submodules.sh
+++ b/t/t5526-fetch-submodules.sh
@@ -428,4 +428,23 @@ test_expect_success "'submodule.<sub>.fetchRecurseSubmodules=on-demand' override
 	test_cmp expect.err.2 actual.err
 '

+test_expect_success "don't fetch submodule when newly recorded commits are already present" '
+	(
+		cd submodule &&
+		git checkout -q HEAD^^
+	) &&
+	head1=$(git rev-parse --short HEAD) &&
+	git add submodule &&
+	git commit -m "submodule rewound" &&
+	head2=$(git rev-parse --short HEAD) &&
+	echo "From $pwd/." > expect.err &&
+	echo "   $head1..$head2  master     -> origin/master" >> expect.err &&
+	(
+		cd downstream &&
+		git fetch >../actual.out 2>../actual.err
+	) &&
+	! test -s actual.out &&
+	test_cmp expect.err actual.err
+'
+
 test_done
-- 
1.7.4.1.190.g13e20