util: make atomictempfile saner if mktempcopy fails

merged with crew-stable

util: import random, missing since ea82a23cf887

clone: try updating to the actual changeset specified in options When cloning with the -r option or # url format from a tag the destination repo most likely won't have the tag. We can save the lookup result to get to the correct parent anyway. Similar to issue1306, but for tags.

commit: hoist the rest of the dirstate manipulation out of commitctx

commit: hoist up dirstate invalidate

commitctx: use contexts more fully

context: add new manifestnode method

commitctx: eliminate some variables

commit: move lots of commitctx outside of the repo lock