test-copies: test that copies' sidedata can get computed during push
If the source of the push does not have the necessary sidedata but the server
needs them, the client should compute them on the fly while pushing.
Differential Revision: https://phab.mercurial-scm.org/D10350
cat >> $HGRCPATH <<EOF
[extensions]
narrow=
[ui]
ssh=$PYTHON "$RUNTESTDIR/dummyssh"
[experimental]
changegroup3 = True
EOF