enter_repo: do not modify input

entr_repo(..., 0) currently modifies the input to strip away
trailing slashes. This means that we some times need to copy the
input to keep the original.

Change it to unconditionally copy it into the used_path buffer so
we can safely use the input without having to copy it. Also store
a working copy in validated_path up-front before we start
resolving anything.

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Phil Hord <hordp@cisco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/daemon.c b/daemon.c
index 4c8346d..9253192 100644
--- a/daemon.c
+++ b/daemon.c
@@ -108,11 +108,11 @@
 	exit(1);
 }
 
-static char *path_ok(char *directory)
+static const char *path_ok(char *directory)
 {
 	static char rpath[PATH_MAX];
 	static char interp_path[PATH_MAX];
-	char *path;
+	const char *path;
 	char *dir;
 
 	dir = directory;