tests/test-commit-copy

patchbomb: fix bug introduced in 4ddfad7ebd98 and add test

Thanks to Augie Fackler for reporting this.

#!/bin/sh

hg init dir
cd dir
echo bleh > bar
hg add bar
hg ci -m 'add bar'

hg cp bar foo
echo >> bar
hg ci -m 'cp bar foo; change bar'

hg debugrename foo
hg debugindex .hg/store/data/bar.i