completion: complete dim retip to local branches

Signed-off-by: Jani Nikula <jani.nikula@intel.com>

bash_completion

@@ -9,6 +9,11 @@ dim ()
 	fi
 }
 
+_dim_git_branches()
+{
+	git for-each-ref --format='%(refname:short)' refs/heads
+}
+
 _dim ()
 {
 	local args arg cur prev words cword split
@@ -107,6 +112,9 @@ _dim ()
 				COMPREPLY=( $( compgen -W "$nightly_branches all" -- $cur ) )
 			fi
 			;;
+		retip)
+			COMPREPLY=($(compgen -W "$(_dim_git_branches)" -- $cur))
+			;;
 	esac
 
 	return 0