Summary:
Fixes T12397. Ref T13164. See PHI801.
Several installs have hit various use cases where the path on disk where Phabricator lives changes at runtime. Currently, `bin/ssh-auth` caches a flat file which includes the path to `bin/ssh-exec`, so this may fall out of date if `phabricator/` moves.
These use cases have varying strengths of legitimacy, but "we're migrating to a new set of hosts and the pool is half old machines and half new machines" seems reasonably compelling and not a problem entirely of one's own making.
Test Plan:
- Compared output on `master` to output after change, found them byte-for-byte identical.
- Moved `phabricator/` to `phabricator2/`, ran `bin/ssh-auth`, got updated output.
- Added a new SSH key, saw it appear in the output.
- Grepped for `AUTHFILE_CACHEKEY` (no hits).
- Dropped the cache, verified that the file regenerates cleanly.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13164, T12397
Differential Revision: https://secure.phabricator.com/D19568
6df278bea8