Query for closest public revision instead of mergebase with master
Summary: As discussed in https://fb.facebook.com/groups/scm/permalink/
1887571897959088/: public commit != ancestor of master. We'll still get some "wrong" results from Watchman aware subscriptions in monitor that I can't fix, but this will at least reduce the surface area while they think about how to fix it on their side.
Reviewed By: pittsw
Differential Revision:
D13013085
fbshipit-source-id:
cae9130ec4c4df8ef9a5031a29f5041d58a42920