Auto merge of #87532 - tlyu:bootstrap-rev-list, r=jyn514

Auto merge of #87532 - tlyu:bootstrap-rev-list, r=jyn514

bootstrap.py: use `git rev-list` for robustness

Use `git rev-list` instead of `git log` to be more robust against
UI changes in git. Also, use the full email address for bors,
because `--author` uses a substring match.

Based on #87513, but is separate because it's less minimal and may require additional manual testing.

~Open questions:~
* ~Should the `merge_base` search also use `--first-parent`?~
* ~Do we exclude non-merge commits from bors? There are a few, and I'm not sure what they have in common. Some of them look like squashes, and some look like they're in rollup branches.~

r? `@jyn514`
`@rustbot` label +A-rustbuild +C-cleanup