[PATCH 3/6] check_filename(): use skip_prefix

[Jeff King <peff@peff.net>]

This avoids some magic numbers (and we'll be adding more
similar calls in a minute).

Signed-off-by: Jeff King <peff@peff.net>
---
 setup.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/setup.c b/setup.c
index 000ffa810..f2a8070bd 100644
--- a/setup.c
+++ b/setup.c
@@ -137,10 +137,9 @@ int check_filename(const char *prefix, const char *arg)
 	char *to_free = NULL;
 	struct stat st;
 
-	if (starts_with(arg, ":/")) {
-		if (arg[2] == '\0') /* ":/" is root dir, always exists */
+	if (skip_prefix(arg, ":/", &arg)) {
+		if (!*arg) /* ":/" is root dir, always exists */
 			return 1;
-		arg += 2;
 		prefix = NULL;
 	}
 
-- 
2.13.0.496.ge44ba89db