amend: allow aborting an `amend --patch` by saving an empty file (issue5925) This patch fixes issue5925 by allow aborting a `hg amend --patch` call by saving an empty patch file. This is similar to aborting of `hg amend` when commit message is empty. Test changes demonstrate the fix.

. $TESTDIR/testlib/pythonpath.sh

mkcommit() {
   echo "$1" > "$1"
   hg add "$1"
   hg ci -m "$1"
}

getid() {
   hg log --hidden --template '{node}\n' --rev "$1"
}

cat >> $HGRCPATH <<EOF
[alias]
debugobsolete=debugobsolete -d '0 0'
EOF