tests/test-rebuildstate

verify: fix "missing revlog!" errors for revlog format v0 and add test

With revlog format v0 the .d files are empty if the only revision stored is an
empty file. Since Mercurial can no longer create format v0 repositories, but
still use it, add a script which creates a repository with a single empty file.
This can be used in other tests if wanted.

#!/bin/sh
# basic test for hg debugrebuildstate

hg init repo
cd repo

touch foo bar
hg ci -Am 'add foo bar'

touch baz
hg add baz
hg rm bar

hg debugrebuildstate
echo '% state dump after'
hg debugstate --nodates | sort
echo '% status'
hg st -A