workers: add config to enable/diable workers This adds config to disable/enable workers with default being enabled. Test Plan: enabled profile without updaing .hg/hgrc (the default should be to use workers) and ran hg sprase --enable-profile <profile>.sparse Watched in the proces explorer that hg started 12 new threads for materializing files (this is my worker.numcpus) value Added [worker] enabled = False to the .hg/hgrc and re ran the command. This time hg didn't spawn any new threads for matreializing of files Differential Revision: https://phab.mercurial-scm.org/D1460

diff: disable diff.noprefix option for diffstat (issue5759) We could use patch.diffhunks() instead of patch.diff() to get filenames without parsing patch content, but that isn't always possible because we sometimes feed raw patch data to patch.diffstat().

hgweb: disable diff.noprefix option for diffstat Copied from cf1e15f91c90.