quote_path: give flags parameter to quote_path()

The quote_path() function computes a path (relative to its base
directory) and c-quotes the result if necessary.  Teach it to take a
flags parameter to allow its behaviour to be enriched later.

No behaviour change intended.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

quote.c

@@ -352,7 +352,7 @@ void write_name_quoted_relative(const char *name, const char *prefix,
 }
 
 /* quote path as relative to the given prefix */
-char *quote_path(const char *in, const char *prefix, struct strbuf *out)
+char *quote_path(const char *in, const char *prefix, struct strbuf *out, unsigned flags)
 {
 	struct strbuf sb = STRBUF_INIT;
 	const char *rel = relative_path(in, prefix, &sb);