convert: tell the source repository when a rev has been converted
This lets us roundtrip changes between svn and hg.
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
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% echo hg to svn
scanning source...
sorting...
converting...
0 b
% svn back to hg should do nothing
scanning source...
sorting...
converting...
% hg back to svn should do nothing
scanning source...
sorting...
converting...