Allow modern hunks to be stored deflated
Summary: Ref T4045. Ref T5179. When saving a modern hunk, deflate it if we have the function and deflating it will save a nontrivial number of bytes.
Test Plan:
- Used bin/hunks migrate to move some hunks over, saw ~70-80% compression on most standard hunks.
- Viewed changesets using compressed hunks.
- Profiled gzinflate() and verified the cost is trivial (<< 1ms) at least for normal diffs.
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Differential Revision: https://secure.phabricator.com/D9292