tests/test-abort-checkin

patch: support diff data loss detection and upgrade

In worst case, generating diff in upgrade mode can be two times more expensive
than generating it in git mode directly: we may have to regenerate the whole
diff again whenever a git feature is detected. Also, the first diff attempt is
completely buffered instead of being streamed. That said, even without having
profiled it yet, I am convinced we can fast-path the upgrade mode if necessary
were it to be used in regular diff commands, and not only in mq where avoiding
data loss is worth the price.

#!/bin/sh

cat > abortcommit.py <<EOF
from mercurial import util

def hook(**args):
    raise util.Abort("no commits allowed")

def reposetup(ui, repo):
    repo.ui.setconfig("hooks", "pretxncommit.nocommits", hook)
EOF
abspath=`pwd`/abortcommit.py

echo "[extensions]" >> $HGRCPATH
echo "mq=" >> $HGRCPATH
echo "abortcommit = $abspath" >> $HGRCPATH

hg init foo
cd foo
echo foo > foo
hg add foo

# mq may keep a reference to the repository so __del__ will not be called
# and .hg/journal.dirstate will not be deleted:
hg ci -m foo
hg ci -m foo

exit 0