push: introduce new push.default mode "simple"

When calling "git push" without argument, we want to allow Git to do
something simple to explain and safe. push.default=matching is unsafe
when used to push to shared repositories, and hard to explain to
beginners in some contexts. It is debatable whether 'upstream' or
'current' is the safest or the easiest to explain, so introduce a new
mode called 'simple' that is the intersection of them: push to the
upstream branch, but only if it has the same name remotely. If not, give
an error that suggests the right command to push explicitely to
'upstream' or 'current'.

A question is whether to allow pushing when no upstream is configured. An
argument in favor of allowing the push is that it makes the new mode work
in more cases. On the other hand, refusing to push when no upstream is
configured encourages the user to set the upstream, which will be
beneficial on the next pull. Lacking better argument, we chose to deny
the push, because it will be easier to change in the future if someone
shows us wrong.

Original-patch-by: Jeff King <peff@peff.net>
Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 45 insertions, 2 deletions

diff --git a/builtin/push.c b/builtin/push.c
index 693671315..08ccb891c 100644
--- a/builtin/push.c
+++ b/builtin/push.c
@@ -76,7 +76,44 @@ static int push_url_of_remote(struct remote *remote, const char ***url_p)
 	return remote->url_nr;
 }
 
-static void setup_push_upstream(struct remote *remote)
+static NORETURN int die_push_simple(struct branch *branch, struct remote *remote) {
+	/*
+	 * There's no point in using shorten_unambiguous_ref here,
+	 * as the ambiguity would be on the remote side, not what
+	 * we have locally. Plus, this is supposed to be the simple
+	 * mode. If the user is doing something crazy like setting
+	 * upstream to a non-branch, we should probably be showing
+	 * them the big ugly fully qualified ref.
+	 */
+	const char *advice_maybe = "";
+	const char *short_upstream =
+		skip_prefix(branch->merge[0]->src, "refs/heads/");
+
+	if (!short_upstream)
+		short_upstream = branch->merge[0]->src;
+	/*
+	 * Don't show advice for people who explicitely set
+	 * push.default.
+	 */
+	if (push_default == PUSH_DEFAULT_UNSPECIFIED)
+		advice_maybe = _("\n"
+				 "To choose either option permanently, "
+				 "see push.default in 'git help config'.");
+	die(_("The upstream branch of your current branch does not match\n"
+	      "the name of your current branch.  To push to the upstream branch\n"
+	      "on the remote, use\n"
+	      "\n"
+	      "    git push %s HEAD:%s\n"
+	      "\n"
+	      "To push to the branch of the same name on the remote, use\n"
+	      "\n"
+	      "    git push %s %s\n"
+	      "%s"),
+	    remote->name, short_upstream,
+	    remote->name, branch->name, advice_maybe);
+}
+
+static void setup_push_upstream(struct remote *remote, int simple)
 {
 	struct strbuf refspec = STRBUF_INIT;
 	struct branch *branch = branch_get(NULL);
@@ -103,6 +140,8 @@ static void setup_push_upstream(struct remote *remote)
 		      "your current branch '%s', without telling me what to push\n"
 		      "to update which remote branch."),
 		    remote->name, branch->name);
+	if (simple && strcmp(branch->refname, branch->merge[0]->src))
+		die_push_simple(branch, remote);
 
 	strbuf_addf(&refspec, "%s:%s", branch->name, branch->merge[0]->src);
 	add_refspec(refspec.buf);
@@ -119,8 +158,12 @@ static void setup_default_push_refspecs(struct remote *remote)
 		add_refspec(":");
 		break;
 
+	case PUSH_DEFAULT_SIMPLE:
+		setup_push_upstream(remote, 1);
+		break;
+
 	case PUSH_DEFAULT_UPSTREAM:
-		setup_push_upstream(remote);
+		setup_push_upstream(remote, 0);
 		break;
 
 	case PUSH_DEFAULT_CURRENT: