tests/test-diff-reverse.t

tests: run "cwd was removed" test only if cwd can actually be removed

On some platforms, cwd can't be removed. In which case, util.unlinkpath()
continues with no error since the failure of directory removal isn't critical.
So it doesn't make sense to run the test added by 90a6c18a7c1d on those
platforms. OTOH, we need to run the test in test-rebase-scenario-global.t
since the repository is referenced after that.

  $ hg init

  $ cat > a <<EOF
  > a
  > b
  > c
  > EOF
  $ hg ci -Am adda
  adding a

  $ cat > a <<EOF
  > d
  > e
  > f
  > EOF
  $ hg ci -m moda

  $ hg diff --reverse -r0 -r1
  diff -r 2855cdcfcbb7 -r 8e1805a3cf6e a
  --- a/a	Thu Jan 01 00:00:00 1970 +0000
  +++ b/a	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,3 +1,3 @@
  -d
  -e
  -f
  +a
  +b
  +c

  $ cat >> a <<EOF
  > g
  > h
  > EOF
  $ hg diff --reverse --nodates
  diff -r 2855cdcfcbb7 a
  --- a/a
  +++ b/a
  @@ -1,5 +1,3 @@
   d
   e
   f
  -g
  -h

should show removed file 'a' as being added
  $ hg revert a
  $ hg rm a
  $ hg diff --reverse --nodates a
  diff -r 2855cdcfcbb7 a
  --- /dev/null
  +++ b/a
  @@ -0,0 +1,3 @@
  +d
  +e
  +f

should show added file 'b' as being removed
  $ echo b >> b
  $ hg add b
  $ hg diff --reverse --nodates b
  diff -r 2855cdcfcbb7 b
  --- a/b
  +++ /dev/null
  @@ -1,1 +0,0 @@
  -b