bundlerepo: use raw revision in revdiff()
This is similar to "revlog: use raw revisions in revdiff". revdiff()
generates raw text used in revlog directly.
This makes test-flagprocessor.t happy.
$ hg init
$ echo This is file a1 > a
$ hg add a
$ hg commit -m "commit #0"
$ ls
a
$ echo This is file b1 > b
$ hg add b
$ hg commit -m "commit #1"
$ hg co 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
B should disappear
$ ls
a