tests/test-username-newline.t

revset: changed last implementation to use lazy classes

Instead of using getitem just reverse the revision list and get the first
'lim' elements. With classes like spanset which are easily reversible this
will work faster.

Performance Benchmarking:

$ time hg log -qr "last(all())"
...

real  0m0.569s
user  0m0.447s
sys 0m0.122s

$ time ./hg log -qr "last(all())"
...

real  0m0.215s
user  0m0.150s
sys 0m0.063s

  $ hg init
  $ touch a

  $ unset HGUSER
  $ echo "[ui]" >> .hg/hgrc
  $ echo "username= foo" >> .hg/hgrc
  $ echo "          bar1" >> .hg/hgrc

  $ hg ci -Am m
  adding a
  abort: username 'foo\nbar1' contains a newline
  
  [255]
  $ rm .hg/hgrc

  $ HGUSER=`(echo foo; echo bar2)` hg ci -Am m
  abort: username 'foo\nbar2' contains a newline
  
  [255]
  $ hg ci -Am m -u "`(echo foo; echo bar3)`"
  transaction abort!
  rollback completed
  abort: username 'foo\nbar3' contains a newline!
  [255]