Add git cl bash completition.

README.git-cl.md

 # git-cl
 
 The git-cl README describes the git-cl command set. This document describes how
 code review and git work together in general, intended for people familiar with
 git but unfamiliar with the code review process supported by Rietveld and
 Gerrit.
 
 
 ## Reitveld concepts and terms
 
@@ skipping 79 matching lines @@
 
        O---A---B---C
             \   \   \
              A'--B'--C'
 
    Which is ugly, but it accurately tracks the real history of your work, can be
    thrown away at the end by committing A+A' as a single `squash` commit.
 
 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.