clone: allow cloning local paths with colons in them

Usually "foo:bar" is interpreted as an ssh url. This patch allows to
clone from such paths by putting at least one slash before the colon
(i.e. /path/to/foo:bar or just ./foo:bar).

file://foo:bar should also work, but local optimizations are off in
that case, which may be unwanted. While at there, warn the users about
--local being ignored in this case.

Reported-by: William Giokas <1007380@gmail.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/urls.txt

@@ -23,6 +23,12 @@ An alternative scp-like syntax may also be used with the ssh protocol:
 
 - {startsb}user@{endsb}host.xz:path/to/repo.git/
 
+This syntax is only recognized if there are no slashes before the
+first colon. This helps differentiate a local path that contains a
+colon. For example the local path `foo:bar` could be specified as an
+absolute path or `./foo:bar` to avoid being misinterpreted as an ssh
+url.
+
 The ssh and git protocols additionally support ~username expansion:
 
 - ssh://{startsb}user@{endsb}host.xz{startsb}:port{endsb}/~{startsb}user{endsb}/path/to/repo.git/

builtin/clone.c

@@ -724,6 +724,8 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	is_local = option_local != 0 && path && !is_bundle;
 	if (is_local && option_depth)
 		warning(_("--depth is ignored in local clones; use file:// instead."));
+	if (option_local > 0 && !is_local)
+		warning(_("--local is ignored"));
 
 	if (argc == 2)
 		dir = xstrdup(argv[1]);

connect.c

@@ -550,8 +550,11 @@ struct child_process *git_connect(int fd[2], const char *url_orig,
 	path = strchr(end, c);
 	if (path && !has_dos_drive_prefix(end)) {
 		if (c == ':') {
-			protocol = PROTO_SSH;
-			*path++ = '\0';
+			if (path < strchrnul(host, '/')) {
+				protocol = PROTO_SSH;
+				*path++ = '\0';
+			} else /* '/' in the host part, assume local path */
+				path = end;
 		}
 	} else
 		path = end;

t/t5601-clone.sh

@@ -280,4 +280,9 @@ test_expect_success 'clone checking out a tag' '
 	test_cmp fetch.expected fetch.actual
 '
 
+test_expect_success NOT_MINGW,NOT_CYGWIN 'clone local path foo:bar' '
+	cp -R src "foo:bar" &&
+	git clone "./foo:bar" foobar
+'
+
 test_done