[PATCH] submodule: use cheaper check for submodule pushes

[Stefan Beller <sbeller@google.com>]

In the function push_submodule[1] we use add_submodule_odb[2] to determine
if a submodule has been populated. However the function does not work with
the submodules objects that are added, instead a new child process is used
to perform the actual push in the submodule.

Use is_submodule_populated[3] that is cheaper to guard from unpopulated
submodules.

[1] 'push_submodule' was added in eb21c732d6 (push: teach
    --recurse-submodules the on-demand option, 2012-03-29)
[2] 'add_submodule_odb' was introduced in 752c0c2492 (Add the
    --submodule option to the diff option family, 2009-10-19)
[3] 'is_submodule_populated' was added in 5688c28d81 (submodules:
    add helper to determine if a submodule is populated, 2016-12-16)

Signed-off-by: Stefan Beller <sbeller@google.com>
---
 submodule.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/submodule.c b/submodule.c
index da2b484879..55afad3e8c 100644
--- a/submodule.c
+++ b/submodule.c
@@ -976,7 +976,9 @@ static int push_submodule(const char *path,
 			  const struct string_list *push_options,
 			  int dry_run)
 {
-	if (add_submodule_odb(path))
+	int code;
+
+	if (!is_submodule_populated_gently(path, &code))
 		return 1;
 
 	if (for_each_remote_ref_submodule(path, has_remote, NULL) > 0) {
-- 
2.13.2.695.g117ddefdb4