push: suggest <remote> <branch> when a slash slips into the repository

"git push origin/main" treats "origin/main" as a repository, builds an
anonymous remote from it, and fails later with "'origin/main' does not
appear to be a git repository", giving no hint that the remote and the
branch are separate arguments.

When the repository argument does not name an existing path, is not a
configured remote, and its part before the first slash names one,
suggest the intended "git push <remote> <branch>" form. Skipping the
suggestion when the argument is an existing path leaves a genuine push
to a local "<remote>/<branch>" directory untouched.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>

Author: HaraldNordgren

builtin/push.c

@@ -8,6 +8,7 @@
 #include "advice.h"
 #include "branch.h"
 #include "config.h"
+#include "dir.h"
 #include "environment.h"
 #include "gettext.h"
 #include "hex.h"
@@ -744,6 +745,19 @@ int cmd_push(int argc,
 
 	if (repo) {
 		if (!add_remote_or_group(repo, &remote_group)) {
+			const char *slash = strchr(repo, '/');
+
+			if (slash && !file_exists(repo)) {
+				struct strbuf name = STRBUF_INIT;
+
+				strbuf_add(&name, repo, slash - repo);
+				if (remote_is_configured(remote_get(name.buf), 0))
+					die(_("'%s' is not a valid push target.\n"
+					      "Did you mean to use: git push %s %s?"),
+					    repo, name.buf, slash + 1);
+				strbuf_release(&name);
+			}
+
 			/*
 			 * Not a configured remote name or group name.
 			 * Try treating it as a direct URL or path, e.g.

t/t5529-push-errors.sh

@@ -54,6 +54,25 @@ test_expect_success 'detect empty remote with targeted refspec' '
 	grep "fatal: bad repository ${SQ}${SQ}" stderr
 '
 
+test_expect_success 'suggest <remote> <branch> for a <remote>/<branch> slip' '
+	test_must_fail git push origin/main 2>stderr &&
+	grep "${SQ}origin/main${SQ} is not a valid push target" stderr &&
+	grep "Did you mean to use: git push origin main?" stderr
+'
+
+test_expect_success 'no suggestion when prefix is not a configured remote' '
+	test_must_fail git push not-a-remote/main 2>stderr &&
+	! grep "Did you mean" stderr
+'
+
+test_expect_success 'no suggestion when the argument is an existing path' '
+	test_when_finished "rm -rf origin" &&
+	git init --bare origin/main &&
+	git push origin/main HEAD:refs/heads/pushed 2>stderr &&
+	! grep "Did you mean" stderr &&
+	git -C origin/main rev-parse --verify refs/heads/pushed
+'
+
 test_expect_success 'detect ambiguous refs early' '
 	git branch foo &&
 	git tag foo &&