Sometimes a txnclose or changegroup hook wants to iterate through all
the changesets in transaction: in that situation usually the revset
`$HG_NODE:` is used to select the revisions. Unfortunately this revset
sometimes may contain too many changesets because we don't have the
write lock while the hook runs newer changes may be added to
repository in the meantime.
That's why there is a need for extra variable carrying the information about
the last change in the transaction.
$TESTDIR is added to the path, so this is superfluous. Also,
inconsistent use of quotes means we might have broken on tests with
paths containing spaces.
We want to keep both code paths tested. The test is a bit too extensive to
simply introduce dual testing in it, so we make a copy for each protocol
version.
