context: avoid writing outdated dirstate out (issue5584) Before this patch, workingctx.status() may cause writing outdated dirstate out, if: - .hg/dirstate is changed simultaneously after last loading it, - there is any file, which should be dirstate.normal()-ed Typical issue case is: - the working directory is updated by "hg update" - .hg/dirstate is updated in background (e.g. fsmonitor) This patch compares identities of dirstate before and after acquisition of wlock, and avoids writing outdated dirstate out, if change of .hg/dirstate is detected.