mercurial/help/phases.txt

filelog: raise CensoredNodeError when hash checks fail with censor metadata

With this change, when a revlog revision hash does not match its content, and
the content is empty with a special metadata key, the integrity failure is
assumed to be intentionally caused to remove sensitive content from repository
history.

To allow different Mercurial functionality to handle this scenario differently
a more specific exception is raised than "ordinary" hash failures.

Alternatives to this approach include, but are not limited to:

- Calling a hook when hashes mismatch to allow arbitrary tombstone validation.
  Cons: Irresponsibly easy to disable integrity checking altogether.
- Returning empty revision data eagerly instead of raising, masking the error.
  Cons: Push/pull won't roundtrip the tombstone, so client repos are unusable.
- Doing nothing differently at this layer. Callers must do their own detection
  of tombstoned data if they want to handle some hash checks and not others.
  - Impacts dozens of callsites, many of which don't have the revision data
  - Would probably be missing one or two callsites at any given time
  - Currently we throw a RevlogError, as do 12 other places in revlog.py.
    Callers would need to parse the exception message and/or ensure
    RevlogError is not thrown from any other part of their call tree.

What are phases?
================

Phases are a system for tracking which changesets have been or should
be shared. This helps prevent common mistakes when modifying history
(for instance, with the mq or rebase extensions).

Each changeset in a repository is in one of the following phases:

 - public : changeset is visible on a public server
 - draft : changeset is not yet published
 - secret : changeset should not be pushed, pulled, or cloned

These phases are ordered (public < draft < secret) and no changeset
can be in a lower phase than its ancestors. For instance, if a
changeset is public, all its ancestors are also public. Lastly,
changeset phases should only be changed towards the public phase.

How are phases managed?
=======================

For the most part, phases should work transparently. By default, a
changeset is created in the draft phase and is moved into the public
phase when it is pushed to another repository.

Once changesets become public, extensions like mq and rebase will
refuse to operate on them to prevent creating duplicate changesets.
Phases can also be manually manipulated with the :hg:`phase` command
if needed. See :hg:`help -v phase` for examples.

Phases and servers
==================

Normally, all servers are ``publishing`` by default. This means::

 - all draft changesets that are pulled or cloned appear in phase
 public on the client

 - all draft changesets that are pushed appear as public on both
 client and server

 - secret changesets are neither pushed, pulled, or cloned

.. note::

  Pulling a draft changeset from a publishing server does not mark it
  as public on the server side due to the read-only nature of pull.

Sometimes it may be desirable to push and pull changesets in the draft
phase to share unfinished work. This can be done by setting a
repository to disable publishing in its configuration file::

  [phases]
  publish = False

See :hg:`help config` for more information on configuration files.

.. note::

  Servers running older versions of Mercurial are treated as
  publishing.

.. note::

   Changesets in secret phase are not exchanged with the server. This
   applies to their content: file names, file contents, and changeset
   metadata. For technical reasons, the identifier (e.g. d825e4025e39)
   of the secret changeset may be communicated to the server.


Examples
========

 - list changesets in draft or secret phase::

     hg log -r "not public()"

 - change all secret changesets to draft::

     hg phase --draft "secret()"

 - forcibly move the current changeset and descendants from public to draft::

     hg phase --force --draft .

 - show a list of changeset revision and phase::

     hg log --template "{rev} {phase}\n"

 - resynchronize draft changesets relative to a remote repository::

     hg phase -fd "outgoing(URL)"

See :hg:`help phase` for more information on manually manipulating phases.