fetch: define shallow boundary with --shallow-exclude

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/fetch-options.txt b/Documentation/fetch-options.txt
index 8738d3d..7aa1285 100644
--- a/Documentation/fetch-options.txt
+++ b/Documentation/fetch-options.txt
@@ -18,6 +18,11 @@
 	Deepen or shorten the history of a shallow repository to
 	include all reachable commits after <date>.
 
+--shallow-exclude=<revision>::
+	Deepen or shorten the history of a shallow repository to
+	exclude commits reachable from a specified remote branch or tag.
+	This option can be specified multiple times.
+
 --unshallow::
 	If the source repository is complete, convert a shallow
 	repository to a complete one, removing all the limitations