tests/notcapable

rebase: allow aborting if last-message.txt is missing

Previously, if .hg/rebasestate existed but .hg/last-message.txt was missing, 'hg
rebase --abort' would say there's no rebase in progress but 'hg checkout foo'
would say 'abort: rebase in progress'. It turns out loading the collapse message
will throw a "no rebase in progress" error if the file doesn't exist, even
though .hg/rebasestate obviously indicates a rebase is in progress.

The fix is to only throw an exception if we're trying to --continue, and to just
eat the issues if we're doing --abort.

This issue is exposed by us writing the rebase state earlier in the process.
This will be used by later patches to ensure the user can appropriately 'hg
rebase --abort' if there's a crash before the first the first commit has
finished rebasing. Tests cover all of this. The only negative affect is we now
require a hg rebase --abort in a very specific exception case, as shown in the
test.

# Disable the $CAP wire protocol capability.

if test -z "$CAP"
then
    echo "CAP environment variable not set."
fi

cat > notcapable-$CAP.py << EOF
from mercurial import extensions, peer, localrepo
def extsetup():
    extensions.wrapfunction(peer.peerrepository, 'capable', wrapcapable)
    extensions.wrapfunction(localrepo.localrepository, 'peer', wrappeer)
def wrapcapable(orig, self, name, *args, **kwargs):
    if name in '$CAP'.split(' '):
        return False
    return orig(self, name, *args, **kwargs)
def wrappeer(orig, self):
    # Since we're disabling some newer features, we need to make sure local
    # repos add in the legacy features again.
    return localrepo.locallegacypeer(self)
EOF

echo '[extensions]' >> $HGRCPATH
echo "notcapable-$CAP = `pwd`/notcapable-$CAP.py" >> $HGRCPATH