dirstate: fix rebuild; add a test
If rebuild calls invalidate, it will just queue a (re)read of the dirstate
file, while what we really want is to empty the current state.
%% no changes
%% no changes
%% uncompressed contents in repo
this is a test
%% uncompress our working dir copy
this is a test
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
%% uncompress our new working dir copy
this is a test