strip: make --keep option not set all dirstate times to 0 hg strip -k was using dirstate.rebuild() which reset all the dirstate entries timestamps to 0. This meant that the next time hg status was run every file was considered to be 'unsure', which caused it to do expensive read operations on every filelog. On a repo with >150,000 files it took 70 seconds when everything was in memory. From a cold cache it took several minutes. The fix is to only reset files that have changed between the working context and the destination context. For reference, --keep means the working directory is left alone during the strip. We have users wanting to use this operation to store their work-in-progress as a commit on a branch while they go work on another branch, then come back later and be able to uncommit that work and continue working. They currently use 'git reset HARD^' to accomplish this in git.