fsck.c: refactor and rename common config callback

Refactor code I recently changed in 1f3299fda9 (fsck: make
fsck_config() re-usable, 2021-01-05) so that I could use fsck's config
callback in mktag in 1f3299fda9 (fsck: make fsck_config() re-usable,
2021-01-05).

I don't know what I was thinking in structuring the code this way, but
it clearly makes no sense to have an fsck_config_internal() at all
just so it can get a fsck_options when git_config() already supports
passing along some void* data.

Let's just make use of that instead, which gets us rid of the two
wrapper functions, and brings fsck's common config callback in line
with other such reusable config callbacks.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/mktag.c b/builtin/mktag.c
index 41a399a..23c4b87 100644
--- a/builtin/mktag.c
+++ b/builtin/mktag.c
@@ -14,11 +14,6 @@ static int option_strict = 1;
 
 static struct fsck_options fsck_options = FSCK_OPTIONS_STRICT;
 
-static int mktag_config(const char *var, const char *value, void *cb)
-{
-	return fsck_config_internal(var, value, cb, &fsck_options);
-}
-
 static int mktag_fsck_error_func(struct fsck_options *o,
 				 const struct object_id *oid,
 				 enum object_type object_type,
@@ -93,7 +88,7 @@ int cmd_mktag(int argc, const char **argv, const char *prefix)
 	fsck_options.error_func = mktag_fsck_error_func;
 	fsck_set_msg_type(&fsck_options, "extraheaderentry", "warn");
 	/* config might set fsck.extraHeaderEntry=* again */
-	git_config(mktag_config, NULL);
+	git_config(git_fsck_config, &fsck_options);
 	if (fsck_tag_standalone(NULL, buf.buf, buf.len, &fsck_options,
 				&tagged_oid, &tagged_type))
 		die(_("tag on stdin did not pass our strict fsck check"));