clean up struct ref's nonfastforward field

Each ref structure contains a "nonfastforward" field which
is set during push to show whether the ref rewound history.
Originally this was a single bit, but it was changed in
f25950f (push: Provide situational hints for non-fast-forward
errors) to an enum differentiating a non-ff of the current
branch versus another branch.

However, we never actually set the member according to the
enum values, nor did we ever read it expecting anything but
a boolean value. But we did use the side effect of declaring
the enum constants to store those values in a totally
different integer variable. The code as-is isn't buggy, but
the enum declaration inside "struct ref" is somewhat
misleading.

Let's convert nonfastforward back into a single bit, and
then define the NON_FF_* constants closer to where they
would be used (they are returned via the "int *nonfastforward"
parameter to transport_push, so we can define them there).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -1009,6 +1009,7 @@ struct ref {
 	char *symref;
 	unsigned int force:1,
 		merge:1,
+		nonfastforward:1,
 		deletion:1;
 	enum {
 		REF_STATUS_NONE = 0,
@@ -1019,10 +1020,6 @@ struct ref {
 		REF_STATUS_REMOTE_REJECT,
 		REF_STATUS_EXPECTING_REPORT
 	} status;
-	enum {
-		NON_FF_HEAD = 1,
-		NON_FF_OTHER
-	} nonfastforward;
 	char *remote_status;
 	struct ref *peer_ref; /* when renaming */
 	char name[FLEX_ARRAY]; /* more */

transport.h

@@ -138,6 +138,8 @@ int transport_set_option(struct transport *transport, const char *name,
 void transport_set_verbosity(struct transport *transport, int verbosity,
 	int force_progress);
 
+#define NON_FF_HEAD 1
+#define NON_FF_OTHER 2
 int transport_push(struct transport *connection,
 		   int refspec_nr, const char **refspec, int flags,
 		   int * nonfastforward);