built-ins: use free() not UNLEAK() if trivial, rm dead code

For a lot of uses of UNLEAK() it would be quite tricky to release the
memory involved, or we're missing the relevant *_(release|clear)()
functions. But in these cases we have them already, and can just
invoke them on the variable(s) involved, instead of UNLEAK().

For "builtin/worktree.c" the UNLEAK() was also added in [1], but the
struct member it's unleaking was removed in [2]. The only non-"int"
member of that structure is "const char *keep_locked", which comes to
us via "argv" or a string literal[3].

We have good visibility via the compiler and
tooling (e.g. SANITIZE=address) on bad free()-ing, but none on
UNLEAK() we don't need anymore. So let's prefer releasing the memory
when it's easy.

For "bugreport", "worktree" and "config" we need to start using a "ret
= ..." return pattern. For "builtin/bugreport.c" these UNLEAK() were
added in [4], and for "builtin/config.c" in [1].

For "config" the code seen here was the only user of the "value"
variable. For "ACTION_{RENAME,REMOVE}_SECTION" we need to be sure to
return the right exit code in the cases where we were relying on
falling through to the top-level.

I think there's still a use-case for UNLEAK(), but hat it's changed
since then. Using it so that "we can see the real leaks" is
counter-productive in these cases.

It's more useful to have UNLEAK() be a marker of the remaining odd
cases where it's hard to free() the memory for whatever reason. With
this change less than 20 of them remain in-tree.

1. 0e5bba53af (add UNLEAK annotation for reducing leak false
   positives, 2017-09-08)
2. d861d34a6e (worktree: remove extra members from struct add_opts,
   2018-04-24)
3. 0db4961c49 (worktree: teach `add` to accept --reason <string> with
  --lock, 2021-07-15)
4. 0e5bba53af and 00d8c31105 (commit: fix "author_ident" leak,
   2022-05-12).

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>

builtin/config.c

@@ -639,8 +639,9 @@ static char *default_user_config(void)
 int cmd_config(int argc, const char **argv, const char *prefix)
 {
 	int nongit = !startup_info->have_repository;
-	char *value;
+	char *value = NULL;
 	int flags = 0;
+	int ret = 0;
 
 	given_config_source.file = xstrdup_or_null(getenv(CONFIG_ENVIRONMENT));
 
@@ -856,44 +857,38 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		free(config_file);
 	}
 	else if (actions == ACTION_SET) {
-		int ret;
 		check_write();
 		check_argc(argc, 2, 2);
 		value = normalize_value(argv[0], argv[1]);
-		UNLEAK(value);
 		ret = git_config_set_in_file_gently(given_config_source.file, argv[0], value);
 		if (ret == CONFIG_NOTHING_SET)
 			error(_("cannot overwrite multiple values with a single value\n"
 			"       Use a regexp, --add or --replace-all to change %s."), argv[0]);
-		return ret;
 	}
 	else if (actions == ACTION_SET_ALL) {
 		check_write();
 		check_argc(argc, 2, 3);
 		value = normalize_value(argv[0], argv[1]);
-		UNLEAK(value);
-		return git_config_set_multivar_in_file_gently(given_config_source.file,
-							      argv[0], value, argv[2],
-							      flags);
+		ret = git_config_set_multivar_in_file_gently(given_config_source.file,
+							     argv[0], value, argv[2],
+							     flags);
 	}
 	else if (actions == ACTION_ADD) {
 		check_write();
 		check_argc(argc, 2, 2);
 		value = normalize_value(argv[0], argv[1]);
-		UNLEAK(value);
-		return git_config_set_multivar_in_file_gently(given_config_source.file,
-							      argv[0], value,
-							      CONFIG_REGEX_NONE,
-							      flags);
+		ret = git_config_set_multivar_in_file_gently(given_config_source.file,
+							     argv[0], value,
+							     CONFIG_REGEX_NONE,
+							     flags);
 	}
 	else if (actions == ACTION_REPLACE_ALL) {
 		check_write();
 		check_argc(argc, 2, 3);
 		value = normalize_value(argv[0], argv[1]);
-		UNLEAK(value);
-		return git_config_set_multivar_in_file_gently(given_config_source.file,
-							      argv[0], value, argv[2],
-							      flags | CONFIG_FLAGS_MULTI_REPLACE);
+		ret = git_config_set_multivar_in_file_gently(given_config_source.file,
+							     argv[0], value, argv[2],
+							     flags | CONFIG_FLAGS_MULTI_REPLACE);
 	}
 	else if (actions == ACTION_GET) {
 		check_argc(argc, 1, 2);
@@ -934,26 +929,28 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 							      flags | CONFIG_FLAGS_MULTI_REPLACE);
 	}
 	else if (actions == ACTION_RENAME_SECTION) {
-		int ret;
 		check_write();
 		check_argc(argc, 2, 2);
 		ret = git_config_rename_section_in_file(given_config_source.file,
 							argv[0], argv[1]);
 		if (ret < 0)
 			return ret;
-		if (ret == 0)
+		else if (!ret)
 			die(_("no such section: %s"), argv[0]);
+		else
+			ret = 0;
 	}
 	else if (actions == ACTION_REMOVE_SECTION) {
-		int ret;
 		check_write();
 		check_argc(argc, 1, 1);
 		ret = git_config_rename_section_in_file(given_config_source.file,
 							argv[0], NULL);
 		if (ret < 0)
 			return ret;
-		if (ret == 0)
+		else if (!ret)
 			die(_("no such section: %s"), argv[0]);
+		else
+			ret = 0;
 	}
 	else if (actions == ACTION_GET_COLOR) {
 		check_argc(argc, 1, 2);
@@ -966,5 +963,6 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		return get_colorbool(argv[0], argc == 2);
 	}
 
-	return 0;
+	free(value);
+	return ret;
 }