hgmerge: add and use more tool variables
This patch adds even more customisable variables with tool paths.
Also moves $FILEMERGE where it belongs.
#!/bin/sh
hg init
echo "[hooks]" > .hg/hgrc
echo 'precommit = echo precommit hook' >> .hg/hgrc
echo 'commit = echo commit hook: $NODE' >> .hg/hgrc
echo 'commit.b = echo commit hook b' >> .hg/hgrc
echo a > a
hg add a
hg commit -m "test" -d "0 0"