R1:4edf8ae2fcb9

make "browse in diffusion" action work for commits in branches other than master

Summary: we do this by passing the "seenOnBranches" commit data detail through the stack

Test Plan: browse in diffusion link worked for non-master checkins under git

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T1949

Differential Revision: https://secure.phabricator.com/D3853