Revert almost all of 5be434785317; add a test
Because of file copies, we should update the manifest dict only after
committing all files.
#!/bin/sh
hg init a
cd a
hg init b
echo x > b/x
echo '# should print nothing'
hg st
echo '# should print ? b/x'
hg st b/x
hg add b/x
echo '# should print A b/x'
hg st
echo '# should forget b/x'
hg revert --all
echo '# should print nothing'
hg st b