error: add CensoredNodeError, will be thrown when content deliberately erased This change introduces the error plus a corresponding catch in dispatch, to provide localized error messages. The verb "censor" is used in this commit and all following to refer to erasing the content of a revlog revision (filelog, for now) without recalculating node IDs, leaving that revision invalid. Further work must be done to safely share such revision data with compliant clients. I find the analogy to censorship straightforward; for less politically charged options, consider "erase", "excise", "expunge", or "blackhole".

files: cache repo.dirstate For a large repo, 'hg files' goes from 2.27 seconds to 1.92.

files: only check for removed, not unknown or missing ctx.matches() doesn't return unknown files, and repo.dirstate[f] never returns '!' for an answer.

files: use ctx.matches instead of ctx.walk ctx.matches() is an optimized form of ctx.walk() when we don't care about the state of files on disk. For a large repo, 'hg files > /dev/null' drops from 3.7 seconds to 2.3.