Fixed a bashism with the use of $RANDOM in hgeditor.
The variable $RANDOM is not POSIX so a portable /bin/sh may not define
it. When creating a directory with a random name it's better to use
mktemp, which, even though is not POSIX, exists in common Unixes
including Linux, OpenBSD, FreeBSD and MacOS X.
#!/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