Merge pull request #1447 from kermit666/image-tag-doc

doc: syntax to run a specific image tag

docs/sources/commandline/command/run.rst

@@ -8,7 +8,7 @@
 
 ::
 
-    Usage: docker run [OPTIONS] IMAGE [COMMAND] [ARG...]
+    Usage: docker run [OPTIONS] IMAGE[:TAG] [COMMAND] [ARG...]
 
     Run a command in a new container