debug-delta-chain: actually skip unrequested computation Doing quick test on mozilla-unified show we can run up to 2× faster by skipping some of these computation.

debug-delta-chain: add options to control what we compute Currently this mostly controls what we display, but actual computation saving will come soon.

debug-delta-chaing: add a parameter to select revision to look at This allows for much faster runtime when we are interrested in some revisions only.

delta-chain: extract some debugdeltachain logic is object Moving from a closure to an object's method will help us to extend the command logic.

delta-chain: move the debugdeltachain command in revlogutils There is a dedicated `mercurial.revlogutils.debug` module were this code fits well.

dirstate: document the `changing_*` context manager The methods that requires them have documentation, but the context themselves had none. This is now fixed.

revlog: deprecate the compatibility config property Now that core is no longer use them, we can deprecated them. Let us aim at removing them in the next version.