largefiles: replace use of synclfdirstate with drop
Replace calling a complex function with a simple dedicated one
Differential Revision: https://phab.mercurial-scm.org/D11113
testing: do not stop waiting if timeout is 0 (
issue6541)
Differential Revision: https://phab.mercurial-scm.org/D11102
largefile: use `parentchange` markcommitted
Differential Revision: https://phab.mercurial-scm.org/D11112