As described in
https://difftastic.wilfred.me.uk/git.html#difftastic-by-default, the
`--ext-diff` option needs to be used for difftastic to be used on
commands other than `git diff`, such as `git show` or `git log`.
> This only applies to git diff. For other git commands, you still need
to specify --ext-diff, or use an alias as described above.
```shell
$ git diff
$ git show HEAD --ext-diff
$ git log -p --ext-diff
```
> Conversely, if you need to copy/paste a diff in the standard diff
format, you can use git diff --no-ext-diff.
Oliver Davies
2fbf67507f