run merge program in repo root.
before, merge program was run in user current directory. Well defined
location is better for scripts. no more need to pass HG_ROOT to merge
program now.
#!/bin/sh
hg init
echo 123 > a
hg add a
hg commit -m "first" -d "0 0" a
mkdir sub
echo 321 > sub/b
hg add sub/b
hg commit -m "second" -d "0 0" sub/b
cat sub/b
hg co 0
cat sub/b
ls sub
true