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)'

Reviewers: dschleimer, btrahan

Reviewed By: dschleimer

CC: aran

Maniphest Tasks: T1268

Differential Revision: https://secure.phabricator.com/D2950