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 a space was meant
instead of a slash.

When the repository argument is not a configured remote and its part
before the first slash names one, suggest the intended
"git push <remote> <branch>" form.

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

Author: HaraldNordgren

builtin/push.c

@@ -744,6 +744,24 @@ int cmd_push(int argc,
 
 	if (repo) {
 		if (!add_remote_or_group(repo, &remote_group)) {
+			const char *slash = strchr(repo, '/');
+
+			/*
+			 * A repository argument of the form
+			 * "<remote>/<branch>" is almost always a slip for
+			 * "<remote> <branch>" rather than a path or URL.
+			 */
+			if (slash) {
+				struct strbuf name = STRBUF_INIT;
+
+				strbuf_add(&name, repo, slash - repo);
+				if (remote_is_configured(remote_get(name.buf), 0))
+					die(_("'%s' does not appear to be a git repository.\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 +54,17 @@ 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} does not appear to be a git repository" 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 'detect ambiguous refs early' '
 	git branch foo &&
 	git tag foo &&