test: improve skipped message for topic The skipped message should point people to a way to solve the situation.

prune: suggest --biject in error "hint" When use specify multiple changesets to prune and as successors, we should point them to the right options to confirm there intend.

metaedit: check for public changeset before instability Public changeset will stay public even if the selection is adjusted, this is a more definitive condition that is worth warning about first.

fold: move sanity check after locking Checking for operation validaty without the locks open us to race condition.

metaedit: add support for folding commits while editing their metadata This also allows us to accept multiple commits without dealing with the thorny algorithmic and UI issues of editing multiple commits at once. Crucially, it is different from 'hg fold --exact' in that it also allows 'folding' a single commit and rewriting its metadata. This is really useful to have as a single logical operation, for example while preparing a series of multiple local changesets that will need to be pushed as a single changeset.

commands: introduce a new command to edit commit metadata This patch introduces metaedit, a command to metadata of a set of revisions without updating the working copy. This is particularly relevant for repositories where changing the parent of the working copy is time-consuming. We could add more stack manipulation operations to metaedit in the future.