Merge branch 'tb/complete-diff-anchored'

The command line completion (in contrib/) learned that "git diff"
takes the "--anchored" option.

* tb/complete-diff-anchored:
  completion: add --anchored to diff's options
diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index b50c5d0..4073d67 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -1729,6 +1729,7 @@
 			--indent-heuristic --no-indent-heuristic
 			--textconv --no-textconv
 			--patch --no-patch
+			--anchored=
 "
 
 __git_diff_difftool_options="--cached --staged --pickaxe-all --pickaxe-regex