tests/test-diff-hashes.t

changegroup: flush the ui stdio buffers after adding a changegroup

This eliminates the following test failure on Windows, as well as a similar one
in evolve's test-wireproto.t.  See the previous patch for details on the
problem.

  --- e:/Projects/hg/tests/test-init.t
  +++ e:/Projects/hg/tests/test-init.t.err
  @@ -216,10 +216,10 @@
      * test                      0:08b9e9f63b32
     $ hg clone -e "python \"$TESTDIR/dummyssh\"" local ssh://user@dummy/remote-bookmarks
     searching for changes
  +  exporting bookmark test
     remote: adding changesets
     remote: adding manifests
     remote: adding file changes
     remote: added 1 changesets with 1 changes to 1 files
  -  exporting bookmark test
     $ hg -R remote-bookmarks bookmarks
        test                      0:08b9e9f63b32

  $ hg init a
  $ cd a

  $ hg diff inexistent1 inexistent2
  inexistent1: * (glob)
  inexistent2: * (glob)

  $ echo bar > foo
  $ hg add foo
  $ hg ci -m 'add foo'

  $ echo foobar > foo
  $ hg ci -m 'change foo'

  $ hg --quiet diff -r 0 -r 1
  --- a/foo	Thu Jan 01 00:00:00 1970 +0000
  +++ b/foo	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,1 @@
  -bar
  +foobar

  $ hg diff -r 0 -r 1
  diff -r a99fb63adac3 -r 9b8568d3af2f foo
  --- a/foo	Thu Jan 01 00:00:00 1970 +0000
  +++ b/foo	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,1 @@
  -bar
  +foobar

  $ hg --verbose diff -r 0 -r 1
  diff -r a99fb63adac3 -r 9b8568d3af2f foo
  --- a/foo	Thu Jan 01 00:00:00 1970 +0000
  +++ b/foo	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,1 @@
  -bar
  +foobar

  $ hg --debug diff -r 0 -r 1
  diff -r a99fb63adac3f31816a22f665bc3b7a7655b30f4 -r 9b8568d3af2f1749445eef03aede868a6f39f210 foo
  --- a/foo	Thu Jan 01 00:00:00 1970 +0000
  +++ b/foo	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,1 @@
  -bar
  +foobar

  $ cd ..