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> Upstream-commit: 2f19e910bdeee94a2962ce8457325e92aa21ce0e Component: engine
2016-07-05 10:02:16 -07:00
parent eff3f9141a
commit 3660e7a630
1 changed files with 2 additions and 1 deletions
@@ -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