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.
Checked out revision 0.
A a
Adding a
Transmitting file data .
Committed revision 1.
% initial roundtrip
scanning source...
sorting...
converting...
0 added a
scanning source...
sorting...
converting...
% second roundtrip should do nothing
scanning source...
sorting...
converting...
scanning source...
sorting...
converting...
% new hg rev
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% adding an empty revision
% echo hg to svn
scanning source...
sorting...
converting...
1 b
0 emtpy
% svn back to hg should do nothing
scanning source...
sorting...
converting...
% hg back to svn should do nothing
scanning source...
sorting...
converting...