graft: reuse the --log value passed initially in `hg graft --continue` (BC)
We now stores the value of --log flag passed initially in the graftstate and
reuse that value when doing `hg graft --continue` which is a nice behavior.
The test updates demonstrate the fix.
Since we now preserve the value by default, drop the mention of `--log` flag
from the hint which we see after conflicts.
Differential Revision: https://phab.mercurial-scm.org/D3662
cat >> $HGRCPATH <<EOF
[extensions]
narrow=
[ui]
ssh=python "$TESTDIR/dummyssh"
[experimental]
changegroup3 = True
EOF