touch: use precheck to validate revision This gives us standard check and standard error message.

prune: use precheck to validate revision This gives us standard check and standard error message.

uncommit: use precheck to validate revision This gives us standard check and standard error message.

amend: use precheck to validate revision This gives us standard check and standard error message.

split: use precheck to validate revision This gives us standard check and standard error message.

precheck: handle rewrite attempt of nullrev This is a common breaking case, so we handle and test it in the generic code.

precheck: update the orphan message to something me generic This will help to reuse it for other commands.

precheck: point to the instability doc when aborting This will help user to understand what is going on.

evolve: document the various instability/troubles We need something to point people at.

precheck: also check for unstability creation

prefetc: point at the offending changeset when aborting We do our best to display comptact but usable information.

precheck: point to 'phase' help when aborting some of the error message already does that. It seems a good idea.

precheck: use 'changesets' in the message instead of 'revisions' This match the message `hg commit --amend` issue in core.

rewriteutil: add a precheck function to validate rewrite beforehand For now this only checks for changeset mutability and this is only used by 'checkfold'. We'll expand the checking and usage as we go.

test: remove reference to the graphlog extension The feature is in core for ages.