One way -M could automate user-visible and non-user-visible improvements is to have separate branches for each type of improvement. -M would email only commits

One way -M could automate user-visible and non-user-visible improvements is to have separate branches for each type of improvement. -M would email only commits in the UVIs branch. (And the master branch would just merge commits from those two separate branches, and contain no original commits.) This would allow UVIs to be chosen at commit-time, rather than manually right before sending the email. (It would be possible but harder to choose UVIs manually right before sending the email, by editing history so those commits were in the right branch.)