config: fix constness of out parameter for git_config_get_expiry()

The type of the out parameter of `git_config_get_expiry()` is a pointer
to a constant string, which creates the impression that ownership of the
returned data wasn't transferred to the caller. This isn't true though
and thus quite misleading.

Adapt the parameter to be of type `char **` and adjust callers
accordingly. While at it, refactor `get_shared_index_expire_date()` to
drop the static `shared_index_expire` variable. It is only used in that
function, and furthermore we would only hit the code where we parse the
expiry date a single time because we already use a static `prepared`
variable to track whether we did parse it.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

builtin/gc.c

@@ -167,9 +167,9 @@ static void gc_config(void)
 	git_config_get_bool("gc.autodetach", &detach_auto);
 	git_config_get_bool("gc.cruftpacks", &cruft_packs);
 	git_config_get_ulong("gc.maxcruftsize", &max_cruft_size);
-	git_config_get_expiry("gc.pruneexpire", &prune_expire);
-	git_config_get_expiry("gc.worktreepruneexpire", &prune_worktrees_expire);
-	git_config_get_expiry("gc.logexpiry", &gc_log_expire);
+	git_config_get_expiry("gc.pruneexpire", (char **) &prune_expire);
+	git_config_get_expiry("gc.worktreepruneexpire", (char **) &prune_worktrees_expire);
+	git_config_get_expiry("gc.logexpiry", (char **) &gc_log_expire);
 
 	git_config_get_ulong("gc.bigpackthreshold", &big_pack_threshold);
 	git_config_get_ulong("pack.deltacachesize", &max_delta_cache_size);

config.c

@@ -2766,9 +2766,9 @@ int git_config_get_pathname(const char *key, char **dest)
 	return repo_config_get_pathname(the_repository, key, dest);
 }
 
-int git_config_get_expiry(const char *key, const char **output)
+int git_config_get_expiry(const char *key, char **output)
 {
-	int ret = git_config_get_string(key, (char **)output);
+	int ret = git_config_get_string(key, output);
 	if (ret)
 		return ret;
 	if (strcmp(*output, "now")) {

config.h

@@ -701,7 +701,7 @@ int git_config_get_split_index(void);
 int git_config_get_max_percent_split_change(void);
 
 /* This dies if the configured or default date is in the future */
-int git_config_get_expiry(const char *key, const char **output);
+int git_config_get_expiry(const char *key, char **output);
 
 /* parse either "this many days" integer, or "5.days.ago" approxidate */
 int git_config_get_expiry_in_days(const char *key, timestamp_t *, timestamp_t now);

read-cache.c

@@ -3176,18 +3176,24 @@ static int write_split_index(struct index_state *istate,
 	return ret;
 }
 
-static const char *shared_index_expire = "2.weeks.ago";
-
 static unsigned long get_shared_index_expire_date(void)
 {
 	static unsigned long shared_index_expire_date;
 	static int shared_index_expire_date_prepared;
 
 	if (!shared_index_expire_date_prepared) {
+		const char *shared_index_expire = "2.weeks.ago";
+		char *value = NULL;
+
 		git_config_get_expiry("splitindex.sharedindexexpire",
-				      &shared_index_expire);
+				      &value);
+		if (value)
+			shared_index_expire = value;
+
 		shared_index_expire_date = approxidate(shared_index_expire);
 		shared_index_expire_date_prepared = 1;
+
+		free(value);
 	}
 
 	return shared_index_expire_date;