Merge branch 'jc/push-reject-reasons'

Improve error and advice messages given locally when "git push"
refuses when it cannot compute fast-forwardness by separating these
cases from the normal "not a fast-forward; merge first and push
again" case.

* jc/push-reject-reasons:
  push: finishing touches to explain REJECT_ALREADY_EXISTS better
  push: introduce REJECT_FETCH_FIRST and REJECT_NEEDS_FORCE
  push: further simplify the logic to assign rejection reason
  push: further clean up fields of "struct ref"

cache.h

@@ -1015,10 +1015,8 @@ struct ref {
 	char *symref;
 	unsigned int
 		force:1,
-		requires_force:1,
+		forced_update:1,
 		merge:1,
-		nonfastforward:1,
-		update:1,
 		deletion:1;
 	enum {
 		REF_STATUS_NONE = 0,
@@ -1026,6 +1024,8 @@ struct ref {
 		REF_STATUS_REJECT_NONFASTFORWARD,
 		REF_STATUS_REJECT_ALREADY_EXISTS,
 		REF_STATUS_REJECT_NODELETE,
+		REF_STATUS_REJECT_FETCH_FIRST,
+		REF_STATUS_REJECT_NEEDS_FORCE,
 		REF_STATUS_UPTODATE,
 		REF_STATUS_REMOTE_REJECT,
 		REF_STATUS_EXPECTING_REPORT