revlog: move references to revlog.hash to inside the revlog class This will make it possible for subclasses to have different hashing schemes when appropriate. I anticipate using this in manifests. Note that there's still one client of mercurial.revlog.hash() outside of revlog: mercurial.context.memctx uses it to construct the file entries in an in-memory manifest. I don't think this will be a problem in the immediate future, so I've left it as-is.

revlog: mark nullhash as module-private No other module should ever need this, so mark it with _ so nobody tries to use it.

ui: disable echo back of prompt input if ui is set to non-tty purposely 9ab18a912c44 is nice for test output, but it also affects command-server channel. Command-server client shouldn't receive echo-back message, which makes it harder to parse the output.