Add git cl bash completition.

R=maruel@chromium.org,emso@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2269593002

README.git-cl.md

@@ -97,3 +97,16 @@ then need to change A?
 
 In practice, this comes up pretty rarely. Suggestions for better workflows are
 welcome.
+
+## Bash auto complition
+
+1. Ensure that your base git commands are autocompleted
+[doc](https://git-scm.com/book/en/v1/Git-Basics-Tips-and-Tricks).
+2. Add this to your .bashrc:
+    
+        # The next line enables bash completion for git cl.
+        if [ -f "$HOME/bin/depot_tools/git_cl_completion.sh" ]; then
+          . "$HOME/bin/depot_tools/git_cl_completion.sh"
+        fi
+        
+3. Profit.

git_cl_completion.sh

+# Copyright (c) 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+
+# This adds completion to bash shells for git cl commands. It is
+# meant for developers and not needed for inclusion by any automated
+# processes that will, of course, specify the full command, not rely
+# on or benefit from tab-completion.
+#
+# Requires:
+#   Installed git bash completion.
+#
+# Usage:
+#   Put something like the following in your .bashrc:
+#   . $PATH_TO_DEPOT_TOOLS/git cl_completion.sh
+#
+
+
+# Parses commands from git cl -h.
+__git_cl_commands () {
+  git cl -h 2> /dev/null | sed -n 's/^\s*\x1b\[32m\(.*\)\x1b\[39m.*$/\1/p'
+}
+
+# Caches variables in __git_cl_all_commands.
+__git_cl_compute_all_commands () {
+  test -n "$__git_cl_all_commands" ||
+  __git_cl_all_commands="$(__git_cl_commands)"
+}
+
+_git_cl () {
+  __git_cl_compute_all_commands
+  __gitcomp_nl "$(__git_cl_commands)"
+}