`mumi send-email' only works with patch files. For example, `mumi send-email foo.patch bar.patch'. It would be nice if it could also handle refs like `mumi send-email HEAD~5'.
Here's one way to achieve this. 1. When passed a ref, `mumi send-email' must run `git format-patch' internally to produce patch files, preferably in a temporary directory. 2. Then, `mumi send-email' must send those patches as usual and clean up the temporary directory.
