submodule: improve submodule_has_commits()

Teach 'submodule_has_commits()' to ensure that if a commit exists in a
submodule, that it is also reachable from a ref.

This is a preparatory step prior to merging the logic which checks for
changed submodules when fetching or pushing.

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

diff --git a/submodule.c b/submodule.c
index 3bcf44521b609aa02b5e4de034c942d002f412ec..057695e645342bedef3195f14e33a7a708baae69 100644 (file)
--- a/submodule.c
+++ b/submodule.c
@@ -644,10 +644,44 @@ static int submodule_has_commits(const char *path, struct oid_array *commits)
 {
        int has_commit = 1;
 
+       /*
+        * Perform a cheap, but incorrect check for the existance of 'commits'.
+        * This is done by adding the submodule's object store to the in-core
+        * object store, and then querying for each commit's existance.  If we
+        * do not have the commit object anywhere, there is no chance we have
+        * it in the object store of the correct submodule and have it
+        * reachable from a ref, so we can fail early without spawning rev-list
+        * which is expensive.
+        */
        if (add_submodule_odb(path))
                return 0;
 
        oid_array_for_each_unique(commits, check_has_commit, &has_commit);
+
+       if (has_commit) {
+               /*
+                * Even if the submodule is checked out and the commit is
+                * present, make sure it exists in the submodule's object store
+                * and that it is reachable from a ref.
+                */
+               struct child_process cp = CHILD_PROCESS_INIT;
+               struct strbuf out = STRBUF_INIT;
+
+               argv_array_pushl(&cp.args, "rev-list", "-n", "1", NULL);
+               oid_array_for_each_unique(commits, append_oid_to_argv, &cp.args);
+               argv_array_pushl(&cp.args, "--not", "--all", NULL);
+
+               prepare_submodule_repo_env(&cp.env_array);
+               cp.git_cmd = 1;
+               cp.no_stdin = 1;
+               cp.dir = path;
+
+               if (capture_command(&cp, &out, GIT_MAX_HEXSZ + 1) || out.len)
+                       has_commit = 0;
+
+               strbuf_release(&out);
+       }
+
        return has_commit;
 }