assume parse_commit checks for NULL commit

The parse_commit function will check whether it was passed a
NULL commit pointer, and if so, return an error. There is no
need for callers to check this separately.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin/branch.c

@@ -490,7 +490,7 @@ static void add_verbose_info(struct strbuf *out, struct ref_item *item,
 	const char *sub = _(" **** invalid ref ****");
 	struct commit *commit = item->commit;
 
-	if (commit && !parse_commit(commit)) {
+	if (!parse_commit(commit)) {
 		pp_commit_easy(CMIT_FMT_ONELINE, commit, &subject);
 		sub = subject.buf;
 	}

builtin/commit.c

@@ -1311,7 +1311,7 @@ static void print_summary(const char *prefix, const unsigned char *sha1,
 	commit = lookup_commit(sha1);
 	if (!commit)
 		die(_("couldn't look up newly created commit"));
-	if (!commit || parse_commit(commit))
+	if (parse_commit(commit))
 		die(_("could not parse newly created commit"));
 
 	strbuf_addstr(&format, "format:%h] %s");
@@ -1503,7 +1503,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 		current_head = NULL;
 	else {
 		current_head = lookup_commit_or_die(sha1, "HEAD");
-		if (!current_head || parse_commit(current_head))
+		if (parse_commit(current_head))
 			die(_("could not parse HEAD commit"));
 	}
 	argc = parse_and_validate_options(argc, argv, builtin_commit_options,

commit.c

@@ -79,7 +79,7 @@ struct commit *lookup_commit_reference_by_name(const char *name)
 	if (get_sha1_committish(name, sha1))
 		return NULL;
 	commit = lookup_commit_reference(sha1);
-	if (!commit || parse_commit(commit))
+	if (parse_commit(commit))
 		return NULL;
 	return commit;
 }

notes-utils.c

@@ -18,7 +18,7 @@ void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
 		unsigned char parent_sha1[20];
 		if (!read_ref(t->ref, parent_sha1)) {
 			struct commit *parent = lookup_commit(parent_sha1);
-			if (!parent || parse_commit(parent))
+			if (parse_commit(parent))
 				die("Failed to find/parse commit %s", t->ref);
 			commit_list_insert(parent, &parents);
 		}

sha1_name.c

@@ -582,8 +582,6 @@ static int get_parent(const char *name, int len,
 	if (ret)
 		return ret;
 	commit = lookup_commit_reference(sha1);
-	if (!commit)
-		return -1;
 	if (parse_commit(commit))
 		return -1;
 	if (!idx) {