phabricator: abort if phabsend gets empty revs Previously we didn't abort. Now we abort if revs is empty. This is consistent with "hg export" behavior. Maybe "return 1" is also a reasonable behavior, but that's inconsistent with the existing "hg export".

phabricator: do not upload new diff if nothing changes Previously, `phabsend` uploads new diffs as long as the commit hash changes. That's suboptimal because sometimes the diff is exactly the same as before, the commit hash change is caused by a parent hash change, or commit message change which do not affect diff content. This patch adds a check examining actual diff contents to skip uploading new diffs in that case.