push: point to 'git pull' and 'git push --force' in case of non-fast forward

'git push' failing because of non-fast forward is a very common situation,
and a beginner does not necessarily understand "fast forward" immediately.

Add a new section to the git-push documentation and refer them to it.

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Nanako Shiraishi <nanako3@lavabit.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/builtin-push.c b/builtin-push.c
index 1d92e22f0a..50328f4b08 100644
--- a/builtin-push.c
+++ b/builtin-push.c
@@ -140,6 +140,7 @@ static int do_push(const char *repo, int flags)
 		struct transport *transport =
 			transport_get(remote, url[i]);
 		int err;
+		int nonfastforward;
 		if (receivepack)
 			transport_set_option(transport,
 					     TRANS_OPT_RECEIVEPACK, receivepack);
@@ -148,13 +149,19 @@ static int do_push(const char *repo, int flags)
 
 		if (flags & TRANSPORT_PUSH_VERBOSE)
 			fprintf(stderr, "Pushing to %s\n", url[i]);
-		err = transport_push(transport, refspec_nr, refspec, flags);
+		err = transport_push(transport, refspec_nr, refspec, flags,
+				     &nonfastforward);
 		err |= transport_disconnect(transport);
 
 		if (!err)
 			continue;
 
 		error("failed to push some refs to '%s'", url[i]);
+		if (nonfastforward) {
+			printf("To prevent you from losing history, non-fast-forward updates were rejected.\n"
+			       "Merge the remote changes before pushing again.\n"
+			       "See 'non-fast forward' section of 'git push --help' for details.\n");
+		}
 		errs++;
 	}
 	return !!errs;