For non-merge git commits, we already have ViewDiff for
displaying patch emails, we can reuse it to display non-merge
git commits.
AFAIK, this is the first web-based git repository viewer
to display the output of "git-patch-id --stable".
It currently fills in the search form box with "patchid:",
but maybe it'll do more than that.
More work will be done to support bidirectional mapping
of commits to emails in the future.