`git diff --help` を見ると
```sh
--name-only
     Show only names of changed files.

--name-status
     Show only names and status of changed files. See the description of the --diff-filter option on what the status letters mean.

--diff-filter=[(A|C|D|M|R|T|U|X|B)...[*]]
     Select only files that are Added (A), Copied (C), Deleted (D), Modified (M), Renamed (R), have their type (i.e. regular file, symlink, submodule, ...) changed (T), are Unmerged (U), are Unknown (X), or have had their pairing Broken
     (B). Any combination of the filter characters (including none) can be used. When * (All-or-none) is added to the combination, all paths are selected if there is any file that matches other criteria in the comparison; if there is no file that matches other criteria, nothing is selected.
```
ということのようですが、 `Modified, Added, Copied, Renamed の更新があった .rb ファイルの名前を表示する` という操作?? ですかね!??