revisions API users: use release_revisions() needing REV_INFO_INIT

Use release_revisions() to various users of "struct rev_list" which
need to have their "struct rev_info" zero-initialized before we can
start using it.

For the bundle.c code see the early exit case added in
3bbbe467f2 (bundle verify: error out if called without an object
database, 2019-05-27).

For the relevant bisect.c code see 45b6370812 (bisect: libify
`check_good_are_ancestors_of_bad` and its dependents, 2020-02-17).

For the submodule.c code see the "goto" on "(!left || !right || !sub)"
added in 8e6df65015 (submodule: refactor show_submodule_summary with
helper function, 2016-08-31).

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

bisect.c

@@ -1010,7 +1010,7 @@ void read_bisect_terms(const char **read_bad, const char **read_good)
  */
 enum bisect_error bisect_next_all(struct repository *r, const char *prefix)
 {
-	struct rev_info revs;
+	struct rev_info revs = REV_INFO_INIT;
 	struct commit_list *tried;
 	int reaches = 0, all = 0, nr, steps;
 	enum bisect_error res = BISECT_OK;
@@ -1035,7 +1035,7 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix)
 
 	res = check_good_are_ancestors_of_bad(r, prefix, no_checkout);
 	if (res)
-		return res;
+		goto cleanup;
 
 	bisect_rev_setup(r, &revs, prefix, "%s", "^%s", 1);
 
@@ -1060,14 +1060,16 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix)
 		       term_good,
 		       term_bad);
 
-		return BISECT_FAILED;
+		res = BISECT_FAILED;
+		goto cleanup;
 	}
 
 	if (!all) {
 		fprintf(stderr, _("No testable commit found.\n"
 			"Maybe you started with bad path arguments?\n"));
 
-		return BISECT_NO_TESTABLE_COMMIT;
+		res = BISECT_NO_TESTABLE_COMMIT;
+		goto cleanup;
 	}
 
 	bisect_rev = &revs.commits->item->object.oid;
@@ -1087,7 +1089,8 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix)
 		 * for negative return values for early returns up
 		 * until the cmd_bisect__helper() caller.
 		 */
-		return BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND;
+		res = BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND;
+		goto cleanup;
 	}
 
 	nr = all - reaches - 1;
@@ -1106,7 +1109,10 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix)
 	/* Clean up objects used, as they will be reused. */
 	repo_clear_commit_marks(r, ALL_REV_FLAGS);
 
-	return bisect_checkout(bisect_rev, no_checkout);
+	res = bisect_checkout(bisect_rev, no_checkout);
+cleanup:
+	release_revisions(&revs);
+	return res;
 }
 
 static inline int log2i(int n)

builtin/submodule--helper.c

@@ -766,7 +766,7 @@ static void status_submodule(const char *path, const struct object_id *ce_oid,
 {
 	char *displaypath;
 	struct strvec diff_files_args = STRVEC_INIT;
-	struct rev_info rev;
+	struct rev_info rev = REV_INFO_INIT;
 	int diff_files_result;
 	struct strbuf buf = STRBUF_INIT;
 	const char *git_dir;
@@ -853,6 +853,7 @@ static void status_submodule(const char *path, const struct object_id *ce_oid,
 cleanup:
 	strvec_clear(&diff_files_args);
 	free(displaypath);
+	release_revisions(&rev);
 }
 
 static void status_submodule_cb(const struct cache_entry *list_item,

bundle.c

@@ -196,14 +196,16 @@ int verify_bundle(struct repository *r,
 	 * to be verbose about the errors
 	 */
 	struct string_list *p = &header->prerequisites;
-	struct rev_info revs;
+	struct rev_info revs = REV_INFO_INIT;
 	const char *argv[] = {NULL, "--all", NULL};
 	struct commit *commit;
 	int i, ret = 0, req_nr;
 	const char *message = _("Repository lacks these prerequisite commits:");
 
-	if (!r || !r->objects || !r->objects->odb)
+	if (!r || !r->objects || !r->objects->odb) {
-		return error(_("need a repository to verify a bundle"));
+		ret = error(_("need a repository to verify a bundle"));
+		goto cleanup;
+	}
 
 	repo_init_revisions(r, &revs, NULL);
 	for (i = 0; i < p->nr; i++) {
@@ -221,7 +223,7 @@ int verify_bundle(struct repository *r,
 		error("%s %s", oid_to_hex(oid), name);
 	}
 	if (revs.pending.nr != p->nr)
-		return ret;
+		goto cleanup;
 	req_nr = revs.pending.nr;
 	setup_revisions(2, argv, &revs, NULL);
 
@@ -284,6 +286,8 @@ int verify_bundle(struct repository *r,
 			printf_ln("The bundle uses this filter: %s",
 				  list_objects_filter_spec(&header->filter));
 	}
+cleanup:
+	release_revisions(&revs);
 	return ret;
 }
 

revision.h

@@ -329,6 +329,25 @@ struct rev_info {
 	struct tmp_objdir *remerge_objdir;
 };
 
+/**
+ * Initialize the "struct rev_info" structure with a macro.
+ *
+ * This will not fully initialize a "struct rev_info", the
+ * repo_init_revisions() function needs to be called before
+ * setup_revisions() and any revision walking takes place.
+ *
+ * Use REV_INFO_INIT to make the "struct rev_info" safe for passing to
+ * release_revisions() when it's inconvenient (e.g. due to a "goto
+ * cleanup" pattern) to arrange for repo_init_revisions() to be called
+ * before release_revisions() is called.
+ *
+ * Initializing with this REV_INFO_INIT is redundant to invoking
+ * repo_init_revisions(). If repo_init_revisions() is guaranteed to be
+ * called before release_revisions() the "struct rev_info" can be left
+ * uninitialized.
+ */
+#define REV_INFO_INIT { 0 }
+
 /**
  * Initialize a rev_info structure with default values. The third parameter may
  * be NULL or can be prefix path, and then the `.prefix` variable will be set
@@ -363,7 +382,7 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs,
 
 /**
  * Free data allocated in a "struct rev_info" after it's been
- * initialized with repo_init_revisions().
+ * initialized with repo_init_revisions() or REV_INFO_INIT.
  */
 void release_revisions(struct rev_info *revs);
 

submodule.c

@@ -638,7 +638,7 @@ void show_submodule_diff_summary(struct diff_options *o, const char *path,
 		struct object_id *one, struct object_id *two,
 		unsigned dirty_submodule)
 {
-	struct rev_info rev;
+	struct rev_info rev = REV_INFO_INIT;
 	struct commit *left = NULL, *right = NULL;
 	struct commit_list *merge_bases = NULL;
 	struct repository *sub;
@@ -665,6 +665,7 @@ void show_submodule_diff_summary(struct diff_options *o, const char *path,
 
 out:
 	free_commit_list(merge_bases);
+	release_revisions(&rev);
 	clear_commit_marks(left, ~0);
 	clear_commit_marks(right, ~0);
 	if (sub) {