completion: complete --ita-invisible-in-index and --ita-visible-in-index

The options --ita-invisible-in-index and --ita-visible-in-index are
listed in diff-options.txt and so are included in the documentation of
commands which include this file (diff, diff-*, log, show, format-patch)
but they only make sense for diffs relating to the index. As such, add
them to '__git_diff_difftool_options' instead of
'__git_diff_common_options' since it makes more sense to add them there.

Signed-off-by: Philippe Blain <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: phil-blain

contrib/completion/git-completion.bash

@@ -1763,6 +1763,7 @@ __git_diff_common_options="--stat --numstat --shortstat --summary
 # Options for diff/difftool
 __git_diff_difftool_options="--cached --staged --pickaxe-all --pickaxe-regex
 			--base --ours --theirs --no-index --relative --merge-base
+			--ita-invisible-in-index --ita-visible-in-index
 			$__git_diff_common_options"
 
 _git_diff ()