Safely Rewriting History

Obsolescence markers make it possible to mark changesets that have been deleted or superset in a new version of the changeset.

Unlike the previous way of handling such changes, by stripping the old changesets from the repository, obsolescence markers can be propagated between repositories. This allows for a safe and simple way of exchanging mutable history and altering it after the fact. Changeset phases are respected, such that only draft and secret changesets can be altered (see "hg hg phases" for details).

Obsolescence is tracked using "obsolete markers", a piece of metadata tracking which changesets have been made obsolete, potential successors for a given changeset, the moment the changeset was marked as obsolete, and the user who performed the rewriting operation. The markers are stored separately from standard changeset data can be exchanged without any of the precursor changesets, preventing unnecessary exchange of obsolescence data.

The complete set of obsolescence markers describes a history of changeset modifications that is orthogonal to the repository history of file modifications. This changeset history allows for detection and automatic resolution of edge cases arising from multiple users rewriting the same part of history concurrently.

Current feature status

This feature is still in development. If you see this help, you have enable an extension that turned this feature on.

Obsolescence markers will be exchanged between repositories that explicitly assert support for the obsolescence feature (this can currently only be done via an extension).