R1:176b4a68a8cf

Fix some mercurial edge cases

Summary:
- Old versions of Mercurial give different output for `hg log -- ''` and `hg log`. Just use `hg log`.
- Branch names with spaces can't be specified in `--rev`. I talked with hstuart in #mercurial and apparently am not crazy.

Test Plan:
- Viewed history of a repository.
- Viewed history of a file.
- Viewed branch `m m m m m 2:ffffffffffff (inactive)`
- Learned that you checkout this branch with `hg checkout ':m m m m m 2:ffffffffffff (inactive)'`…