convert: add bookmark support to common sink/source implementation

dirstate: reset _lastnormal and _lastnormaltime on write, invalidate, and clear

discovery: avoid discovery when local graph is a subset of remote Immediately sends local's heads to the server to check whether the server knows them all. If it does, we can call getbundle immediately. Interesting test output changes are: - added 1 changesets with 0 changes to 1 files (+1 heads) + added 1 changesets with 0 changes to 0 files (+1 heads) -> The new getbundle() actually fixes a bug vs. changegroupsubset() in that it no longer returns unnecessary files when file revs are reused. warning: repository is unrelated + requesting all changes -> The new use of common instead of bases correctly indicates that an unrelated pull gets all changes from the server.