revisions API: don't leak memory on argv elements that need free()-ing

Add a "free_removed_argv_elements" member to "struct
setup_revision_opt", and use it to fix several memory leaks.

We have various memory leaks in APIs that take and munge "const
char **argv", e.g. parse_options(). Sometimes these APIs are given the
"argv" we get to the "main" function, in which case we don't leak
memory, but other times we're giving it the "v" member of a "struct
strvec" we created.

There's several potential ways to fix those sort of leaks, we could
add a "nodup" mode to "struct strvec", which would work for the cases
where we push constant strings to it. But that wouldn't work as soon
as we used strvec_pushf(), or otherwise needed to duplicate or create
a string for that "struct strvec".

Let's instead make it the responsibility of the revisions API. If it's
going to clobber elements of argv it can also free() them, which it
will now do if instructed to do so via "free_removed_argv_elements".

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

bisect.c

@@ -653,6 +653,9 @@ static void bisect_rev_setup(struct repository *r, struct rev_info *revs,
 			     const char *bad_format, const char *good_format,
 			     int read_paths)
 {
+	struct setup_revision_opt opt = {
+		.free_removed_argv_elements = 1,
+	};
 	int i;
 
 	repo_init_revisions(r, revs, prefix);
@@ -669,8 +672,7 @@ static void bisect_rev_setup(struct repository *r, struct rev_info *revs,
 	if (read_paths)
 		read_bisect_paths(rev_argv);
 
-	setup_revisions(rev_argv->nr, rev_argv->v, revs, NULL);
-	/* XXX leak rev_argv, as "revs" may still be pointing to it */
+	setup_revisions(rev_argv->nr, rev_argv->v, revs, &opt);
 }
 
 static void bisect_common(struct rev_info *revs)

builtin/submodule--helper.c

@@ -1104,6 +1104,9 @@ static int compute_summary_module_list(struct object_id *head_oid,
 {
 	struct strvec diff_args = STRVEC_INIT;
 	struct rev_info rev;
+	struct setup_revision_opt opt = {
+		.free_removed_argv_elements = 1,
+	};
 	struct module_cb_list list = MODULE_CB_LIST_INIT;
 	int ret = 0;
 
@@ -1121,7 +1124,7 @@ static int compute_summary_module_list(struct object_id *head_oid,
 	init_revisions(&rev, info->prefix);
 	rev.abbrev = 0;
 	precompose_argv_prefix(diff_args.nr, diff_args.v, NULL);
-	setup_revisions(diff_args.nr, diff_args.v, &rev, NULL);
+	setup_revisions(diff_args.nr, diff_args.v, &rev, &opt);
 	rev.diffopt.output_format = DIFF_FORMAT_NO_OUTPUT | DIFF_FORMAT_CALLBACK;
 	rev.diffopt.format_callback = submodule_summary_callback;
 	rev.diffopt.format_callback_data = &list;

remote.c

@@ -2169,6 +2169,9 @@ static int stat_branch_pair(const char *branch_name, const char *base,
 	struct object_id oid;
 	struct commit *ours, *theirs;
 	struct rev_info revs;
+	struct setup_revision_opt opt = {
+		.free_removed_argv_elements = 1,
+	};
 	struct strvec argv = STRVEC_INIT;
 
 	/* Cannot stat if what we used to build on no longer exists */
@@ -2203,7 +2206,7 @@ static int stat_branch_pair(const char *branch_name, const char *base,
 	strvec_push(&argv, "--");
 
 	repo_init_revisions(the_repository, &revs, NULL);
-	setup_revisions(argv.nr, argv.v, &revs, NULL);
+	setup_revisions(argv.nr, argv.v, &revs, &opt);
 	if (prepare_revision_walk(&revs))
 		die(_("revision walk setup failed"));
 

revision.c

@@ -2784,6 +2784,8 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 			const char *arg = argv[i];
 			if (strcmp(arg, "--"))
 				continue;
+			if (opt && opt->free_removed_argv_elements)
+				free((char *)argv[i]);
 			argv[i] = NULL;
 			argc = i;
 			if (argv[i + 1])

revision.h

@@ -375,7 +375,8 @@ struct setup_revision_opt {
 	const char *def;
 	void (*tweak)(struct rev_info *, struct setup_revision_opt *);
 	unsigned int	assume_dashdash:1,
-			allow_exclude_promisor_objects:1;
+			allow_exclude_promisor_objects:1,
+			free_removed_argv_elements:1;
 	unsigned revarg_opt;
 };
 int setup_revisions(int argc, const char **argv, struct rev_info *revs,

t/t2020-checkout-detach.sh

@@ -4,6 +4,7 @@ test_description='checkout into detached HEAD state'
 GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 check_detached () {