submodule--helper: teach push-check to handle HEADbw/push-options-recursively-to-submodules

In 06bf4ad1d (push: propagate remote and refspec with
--recurse-submodules) push was taught how to propagate a refspec down to
submodules when the '--recurse-submodules' flag is given.  The only refspecs
that are allowed to be propagated are ones which name a ref which exists
in both the superproject and the submodule, with the caveat that 'HEAD'
was disallowed.

This patch teaches push-check (the submodule helper which determines if
a refspec can be propagated to a submodule) to permit propagating 'HEAD'
if and only if the superproject and the submodule both have the same
named branch checked out and the submodule is not in a detached head
state.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 15 insertions, 3 deletions

diff --git a/submodule.c b/submodule.c
index 49ab132d05..1c1339fff7 100644
--- a/submodule.c
+++ b/submodule.c
@@ -828,7 +828,8 @@ static int push_submodule(const char *path,
  * Perform a check in the submodule to see if the remote and refspec work.
  * Die if the submodule can't be pushed.
  */
-static void submodule_push_check(const char *path, const struct remote *remote,
+static void submodule_push_check(const char *path, const char *head,
+				 const struct remote *remote,
 				 const char **refspec, int refspec_nr)
 {
 	struct child_process cp = CHILD_PROCESS_INIT;
@@ -836,6 +837,7 @@ static void submodule_push_check(const char *path, const struct remote *remote,
 
 	argv_array_push(&cp.args, "submodule--helper");
 	argv_array_push(&cp.args, "push-check");
+	argv_array_push(&cp.args, head);
 	argv_array_push(&cp.args, remote->name);
 
 	for (i = 0; i < refspec_nr; i++)
@@ -874,10 +876,20 @@ int push_unpushed_submodules(struct sha1_array *commits,
 	 * won't be propagated due to the remote being unconfigured (e.g. a URL
 	 * instead of a remote name).
 	 */
-	if (remote->origin != REMOTE_UNCONFIGURED)
+	if (remote->origin != REMOTE_UNCONFIGURED) {
+		char *head;
+		struct object_id head_oid;
+
+		head = resolve_refdup("HEAD", 0, head_oid.hash, NULL);
+		if (!head)
+			die(_("Failed to resolve HEAD as a valid ref."));
+
 		for (i = 0; i < needs_pushing.nr; i++)
 			submodule_push_check(needs_pushing.items[i].string,
-					     remote, refspec, refspec_nr);
+					     head, remote,
+					     refspec, refspec_nr);
+		free(head);
+	}
 
 	/* Actually push the submodules */
 	for (i = 0; i < needs_pushing.nr; i++) {