$ cat > patchtool.py <<EOF

  > import sys

  > print 'Using custom patch'

  > if '--binary' in sys.argv:

  >     print '--binary found !'

  > EOF

  $ echo "[ui]" >> $HGRCPATH

  $ echo "patch=python ../patchtool.py" >> $HGRCPATH

  $ hg init a

  $ cd a

  $ echo a > a

  $ hg commit -Ama -d '1 0'

  adding a

  $ echo b >> a

  $ hg commit -Amb -d '2 0'

  $ cd ..

 - patch code does not try to add weird arguments like

 --binary when custom patch commands are used. For instance

 --binary is added by default under win32.

check custom patch options are honored

  $ hg --cwd a export -o ../a.diff tip

  $ hg clone -r 0 a b

  requesting all changes

  adding changesets

  adding manifests

  adding file changes

  added 1 changesets with 1 changes to 1 files

  updating to branch default

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg --cwd b import -v ../a.diff

  applying ../a.diff

  Using custom patch