From da2ad48b92d3f7a832a2c5e7b1f437206493a924 Mon Sep 17 00:00:00 2001
From: Aaron Lehmann <aaron.lehmann@docker.com>
Date: Tue, 5 Jul 2016 09:59:45 -0700
Subject: [PATCH] image spec: Correct set of acceptable characters in tags

The image spec did not match the regexp that validates tags. It
neglected to mention that period and dash characters are allowed in
tags, as long as they are not the first character. It also did not
mention the length limit for tags.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
(cherry picked from commit 2f19e910bdeee94a2962ce8457325e92aa21ce0e)
Signed-off-by: Tibor Vass <tibor@docker.com>
---
 image/spec/v1.1.md | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/image/spec/v1.1.md b/image/spec/v1.1.md
index 181f1fb605..3a32b6bd36 100644
--- a/image/spec/v1.1.md
+++ b/image/spec/v1.1.md
@@ -87,7 +87,8 @@ This specification uses the following terms:
     <dd>
         A tag serves to map a descriptive, user-given name to any single image
         ID. Tag values are limited to the set of characters
-        <code>[a-zA-Z_0-9]</code>.
+        <code>[a-zA-Z0-9_.-]</code>, except they may not start with a <code>.</code>
+        or <code>-</code> character. Tags are limited to 127 characters.
     </dd>
     <dt>
         Repository