repository: remove unnecessary include of path.h

This also made it clear that several .c files that depended upon path.h
were missing a #include for it; add the missing includes while at it.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

strbuf.c

@@ -6,6 +6,7 @@
 #include "hex.h"
 #include "object-name.h"
 #include "refs.h"
+#include "path.h"
 #include "repository.h"
 #include "string-list.h"
 #include "utf8.h"