diff: fix leaking orderfile option

The `orderfile` diff option is being assigned via `OPT_FILENAME()`,
which assigns an allocated string to the variable. We never free it
though, causing a memory leak.

Change the type of the string to `char *` and free it to plug the leak.
This also requires us to use `xstrdup()` to assign the global config to
it in case it is set.

This leak is being hit in t7621, but plugging it alone does not make the
test suite pass.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/diff.c b/diff.c
index 472479eb10..6555b8a32c 100644
--- a/diff.c
+++ b/diff.c
@@ -441,8 +441,10 @@ int git_diff_ui_config(const char *var, const char *value,
 	}
 	if (!strcmp(var, "diff.wordregex"))
 		return git_config_string(&diff_word_regex_cfg, var, value);
-	if (!strcmp(var, "diff.orderfile"))
+	if (!strcmp(var, "diff.orderfile")) {
+		FREE_AND_NULL(diff_order_file_cfg);
 		return git_config_pathname(&diff_order_file_cfg, var, value);
+	}
 
 	if (!strcmp(var, "diff.ignoresubmodules")) {
 		if (!value)
@@ -4775,7 +4777,7 @@ void repo_diff_setup(struct repository *r, struct diff_options *options)
 	if (diff_indent_heuristic)
 		DIFF_XDL_SET(options, INDENT_HEURISTIC);
 
-	options->orderfile = diff_order_file_cfg;
+	options->orderfile = xstrdup_or_null(diff_order_file_cfg);
 
 	if (!options->flags.ignore_submodule_set)
 		options->flags.ignore_untracked_in_submodules = 1;
@@ -6727,6 +6729,7 @@ void diff_free(struct diff_options *options)
 		FREE_AND_NULL(options->objfind);
 	}
 
+	FREE_AND_NULL(options->orderfile);
 	for (size_t i = 0; i < options->anchors_nr; i++)
 		free(options->anchors[i]);
 	FREE_AND_NULL(options->anchors);