bookmarks: Only save undo.bookmarks if bookmarks exist
Otherwise the command will abort when there is no .hg/bookmarks file.
#!/bin/sh
#
# Corrupt an hg repo with a pull started during an aborted commit
#
# Create two repos, so that one of them can pull from the other one.
hg init source
cd source
touch foo
hg add foo
hg ci -m 'add foo'
hg clone . ../corrupted
echo >> foo
hg ci -m 'change foo'
# Add a hook to wait 5 seconds and then abort the commit
cd ../corrupted
echo '[hooks]' >> .hg/hgrc
echo 'pretxncommit = sleep 5; exit 1' >> .hg/hgrc
# start a commit...
touch bar
hg add bar
hg ci -m 'add bar' &
# ... and start a pull while the commit is still running
sleep 1
hg pull ../source 2>/dev/null
# see what happened
wait
hg verify