diff: allow stepping back N commits from the selected refsHEADv1.3.1+16masterdevelop

The ref pickers can only select the exact ref that is shown.
Add an offset input next to each picker (idoff and id2off), whose
value is the number of commits to step back, so any ancestor of a
branch or tag can be compared without typing a rev into the url by
hand.  An apply button submits the values typed there, since text
inputs cannot be auto-submitted on their own; the flip link swaps
the offsets along with the refs, and the file-level links carry
them through.

By default both offsets are empty, meaning the selected refs
themselves.  An empty ref submitted from the form is likewise
treated as no ref instead of triggering a bad object name error.

0 files changed, 0 insertions, 0 deletions