Merge branch 'fc/completion'

* fc/completion:
completion: remove __git_index_file_list_filter()
completion: add space after completed filename
completion: add hack to enable file mode in bash < 4
completion: refactor __git_complete_index_file()
completion: refactor diff_index wrappers
completion: use __gitcompadd for __gitcomp_file
completion; remove unuseful comments
completion: document tilde expansion failure in tests
completion: add file completion tests

diff --cc contrib/completion/git-completion.bash
Simple merge