refs.h: rename the action_on_err constants

Given that these constants are only being used when updating
references, it is inappropriate to give them such generic names as
"DIE_ON_ERR".  So prefix their names with "UPDATE_REFS_".

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/merge.c b/builtin/merge.c
index e15d0e1..7d1d83e 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -398,7 +398,7 @@
 			const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 			update_ref(reflog_message.buf, "HEAD",
 				new_head, head, 0,
-				DIE_ON_ERR);
+				UPDATE_REFS_DIE_ON_ERR);
 			/*
 			 * We ignore errors in 'gc --auto', since the
 			 * user should see them.
@@ -1222,7 +1222,7 @@
 			die(_("%s - not something we can merge"), argv[0]);
 		read_empty(remote_head->object.sha1, 0);
 		update_ref("initial pull", "HEAD", remote_head->object.sha1,
-			   NULL, 0, DIE_ON_ERR);
+			   NULL, 0, UPDATE_REFS_DIE_ON_ERR);
 		goto done;
 	} else {
 		struct strbuf merge_names = STRBUF_INIT;
@@ -1339,7 +1339,7 @@
 	}
 
 	update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
-		   NULL, 0, DIE_ON_ERR);
+		   NULL, 0, UPDATE_REFS_DIE_ON_ERR);
 
 	if (remoteheads && !common)
 		; /* No common ancestors found. We need a real merge. */