[PATCH 3/3] push: add option to push only submodules

[Brandon Williams <bmwill@google.com>]

Teach push the --recurse-submodules=only option.  This enables push to
recursively push all unpushed submodules while leaving the superproject
unpushed.

This is a desirable feature in a scenario where updates to the
superproject are handled automatically by some other means, perhaps a
code review tool.  In this scenario a developer could make a change
which spans multiple submodules and then push their commits for code
review.  Upon completion of the code review, their commits can be
accepted and applied to their respective submodules while the code
review tool can then automatically update the superproject to the most
recent SHA1 of each submodule.  This would eliminate the merge conflicts
in the superproject that could occur if multiple people are contributing
to the same submodule.

Signed-off-by: Brandon Williams <bmwill@google.com>
---
 builtin/push.c                 |  2 ++
 t/t5531-deep-submodule-push.sh | 21 +++++++++++++++++++++
 transport.c                    | 15 +++++++++++----
 transport.h                    |  1 +
 4 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/builtin/push.c b/builtin/push.c
index 3bb9d6b..9433797 100644
--- a/builtin/push.c
+++ b/builtin/push.c
@@ -565,6 +565,8 @@ int cmd_push(int argc, const char **argv, const char *prefix)
 		flags |= TRANSPORT_RECURSE_SUBMODULES_CHECK;
 	else if (recurse_submodules == RECURSE_SUBMODULES_ON_DEMAND)
 		flags |= TRANSPORT_RECURSE_SUBMODULES_ON_DEMAND;
+	else if (recurse_submodules == RECURSE_SUBMODULES_ONLY)
+		flags |= TRANSPORT_RECURSE_SUBMODULES_ONLY;
 
 	if (tags)
 		add_refspec("refs/tags/*");
diff --git a/t/t5531-deep-submodule-push.sh b/t/t5531-deep-submodule-push.sh
index 1524ff5..676d686 100755
--- a/t/t5531-deep-submodule-push.sh
+++ b/t/t5531-deep-submodule-push.sh
@@ -454,4 +454,25 @@ test_expect_success 'push --dry-run does not recursively update submodules' '
 	test_cmp expected_submodule actual_submodule
 '
 
+test_expect_success 'push --dry-run does not recursively update submodules' '
+	git -C work push --dry-run --recurse-submodules=only ../pub.git master &&
+
+	git -C submodule.git rev-parse master >actual_submodule &&
+	git -C pub.git rev-parse master >actual_pub &&
+	test_cmp expected_pub actual_pub &&
+	test_cmp expected_submodule actual_submodule
+'
+
+test_expect_success 'push only unpushed submodules recursively' '
+	git -C pub.git rev-parse master >expected_pub &&
+	git -C work/gar/bage rev-parse master >expected_submodule &&
+
+	git -C work push --recurse-submodules=only ../pub.git master &&
+
+	git -C submodule.git rev-parse master >actual_submodule &&
+	git -C pub.git rev-parse master >actual_pub &&
+	test_cmp expected_submodule actual_submodule &&
+	test_cmp expected_pub actual_pub
+'
+
 test_done
diff --git a/transport.c b/transport.c
index 04e5d66..20ebee8 100644
--- a/transport.c
+++ b/transport.c
@@ -947,7 +947,9 @@ int transport_push(struct transport *transport,
 			if (run_pre_push_hook(transport, remote_refs))
 				return -1;
 
-		if ((flags & TRANSPORT_RECURSE_SUBMODULES_ON_DEMAND) && !is_bare_repository()) {
+		if ((flags & (TRANSPORT_RECURSE_SUBMODULES_ON_DEMAND |
+			      TRANSPORT_RECURSE_SUBMODULES_ONLY)) &&
+		    !is_bare_repository()) {
 			struct ref *ref = remote_refs;
 			struct sha1_array commits = SHA1_ARRAY_INIT;
 
@@ -965,7 +967,8 @@ int transport_push(struct transport *transport,
 		}
 
 		if (((flags & TRANSPORT_RECURSE_SUBMODULES_CHECK) ||
-		     ((flags & TRANSPORT_RECURSE_SUBMODULES_ON_DEMAND) &&
+		     ((flags & (TRANSPORT_RECURSE_SUBMODULES_ON_DEMAND |
+				TRANSPORT_RECURSE_SUBMODULES_ONLY)) &&
 		      !pretend)) && !is_bare_repository()) {
 			struct ref *ref = remote_refs;
 			struct string_list needs_pushing = STRING_LIST_INIT_DUP;
@@ -984,7 +987,10 @@ int transport_push(struct transport *transport,
 			sha1_array_clear(&commits);
 		}
 
-		push_ret = transport->push_refs(transport, remote_refs, flags);
+		if (!(flags & TRANSPORT_RECURSE_SUBMODULES_ONLY))
+			push_ret = transport->push_refs(transport, remote_refs, flags);
+		else
+			push_ret = 0;
 		err = push_had_errors(remote_refs);
 		ret = push_ret | err;
 
@@ -996,7 +1002,8 @@ int transport_push(struct transport *transport,
 		if (flags & TRANSPORT_PUSH_SET_UPSTREAM)
 			set_upstreams(transport, remote_refs, pretend);
 
-		if (!(flags & TRANSPORT_PUSH_DRY_RUN)) {
+		if (!(flags & (TRANSPORT_PUSH_DRY_RUN |
+			       TRANSPORT_RECURSE_SUBMODULES_ONLY))) {
 			struct ref *ref;
 			for (ref = remote_refs; ref; ref = ref->next)
 				transport_update_tracking_ref(transport->remote, ref, verbose);
diff --git a/transport.h b/transport.h
index 1b65458..efd5fb6 100644
--- a/transport.h
+++ b/transport.h
@@ -146,6 +146,7 @@ struct transport {
 #define TRANSPORT_PUSH_CERT_IF_ASKED		(1<<12)
 #define TRANSPORT_PUSH_ATOMIC			(1<<13)
 #define TRANSPORT_PUSH_OPTIONS			(1<<14)
+#define TRANSPORT_RECURSE_SUBMODULES_ONLY	(1<<15)
 
 extern int transport_summary_width(const struct ref *refs);
 
-- 
2.8.0.rc3.226.g39d4020