tests/test-ssh-batch.t

rust: Add a Timestamp struct instead of abusing Duration

`SystemTime` would be the standard library type semantically appropriate
instead of `Duration`.

But since the value is coming from Python as a plain integer and used in
dirstate packing code as an integer, let’s make a type that contains a single
integer instead of using one with sub-second precision.

Differential Revision: https://phab.mercurial-scm.org/D10485

  $ hg init a
  $ cd a
  $ touch a; hg commit -qAm_
  $ hg bookmark $(for i in $($TESTDIR/seq.py 0 20); do echo b$i; done)
  $ hg clone . ../b -q
  $ cd ../b

Checking that when lookup multiple bookmarks in one go, if one of them
fails (thus causing the sshpeer to be stopped), the errors from the
further lookups don't result in tracebacks.

  $ hg pull -r b0 -r nosuchbookmark $(for i in $($TESTDIR/seq.py 1 20); do echo -r b$i; done) -e "\"$PYTHON\" \"$TESTDIR/dummyssh\"" ssh://user@dummy/$(pwd)/../a
  pulling from ssh://user@dummy/$TESTTMP/b/../a
  abort: unknown revision 'nosuchbookmark'
  [255]