tests/test-check-commit.t

util: extract compression code in `mercurial.utils.compression`

The code seems large enough to be worth extracting. This is similar to what was
done for various module in `mercurial/utils/`.

Since None of the compression logic takes a `ui` objet, issuing deprecation
warning is tricky. Luckly the logic does not seems to have many external users.

#require test-repo

Enable obsolescence to avoid the warning issue when obsmarker are found

  $ . "$TESTDIR/helpers-testrepo.sh"

Go back in the hg repo

  $ cd $TESTDIR/..

  $ REVSET='not public() and ::. and not desc("# no-check-commit")'

  $ mkdir "$TESTTMP/p"
  $ REVS=`testrepohg log -r "$REVSET" -T.`
  $ if [ -n "$REVS" ] ; then
  >   testrepohg export --git -o "$TESTTMP/p/%n-%h" -r "$REVSET"
  >   for f in `ls "$TESTTMP/p"`; do
  >      contrib/check-commit < "$TESTTMP/p/$f" > "$TESTTMP/check-commit.out"
  >      if [ $? -ne 0 ]; then
  >          node="${f##*-}"
  >          echo "Revision $node does not comply with rules"
  >          echo '------------------------------------------------------'
  >          cat ${TESTTMP}/check-commit.out
  >          echo
  >     fi
  >   done
  > fi