Document the new gerrit-cherry-pick command

Signed-off-by: Shawn O. Pearce <sop@google.com>

Documentation/cmd-cherry-pick.txt

@@ -0,0 +1,39 @@
+gerrit-cherry-pick
+==================
+
+NAME
+----
+gerrit-cherry-pick - Download and cherry pick one or more changes
+
+SYNOPSIS
+--------
+[verse]
+'gerrit-cherry-pick' <remote> <changeid>...
+
+'gerrit-cherry-pick' \--continue | \--skip | \--abort
+'gerrit-cherry-pick' \--close <remote>
+
+DESCRIPTION
+-----------
+Downloads the listed changes specified on the command line and
+proceeds to cherry-pick them (rewriting commit SHA-1s as it goes)
+onto the current branch.
+
+If a merge failure prevents this from being completely automatic,
+you will be asked to resolve the conflict and restart the command
+with the `\--continue` option.
+
+Change ids may be specified as either the change id (e.g. 1234)
+or as change id slash patch set number (e.g. 1234/8).  If the patch
+set number is not supplied, `/1` is assumed.
+
+OBTAINING
+---------
+To obtain the 'gerrit-cherry-pick' script use scp to copy it to
+your local system:
+
+  $ scp -P 29418 gerrit.example.com:bin/gerrit-cherry-pick ~/bin
+
+GERRIT
+------
+Part of link:index.html[Gerrit Code Review]

Documentation/cmd-index.txt

@@ -1,6 +1,20 @@
 Gerrit2 - Command Line Tool
 ===========================
 
+Client Commands
+---------------
+
+Client commands can be downloaded via scp, and then executed on
+the client system.
+
+link:cmd-cherry-pick.html[gerrit-cherry-pick]::
+  Download and cherry-pick one or more changes (commits).
+
+To download a client command, use scp:
+
+  $ scp -P 29418 review.example.com:bin/gerrit-cherry-pick ~/bin
+
+
 Executing Commands
 ------------------