view mercurial/help/internals/censor.txt @ 35935:00b9e26d727b

sshpeer: establish SSH connection before class instantiation

We want to move the handshake to before peers are created so
we can instantiate a different peer class depending on the
results of the handshake. This necessitates moving the SSH
process invocation to outside the peer class.

As part of the code move, some variables were renamed for
clarity. util.popen4() returns stdin, stdout, and stderr in
their typical file descriptor order. However, stdin and stdout
were being mapped to "pipeo" and "pipei" respectively. "o"
for "stdin" and "i" for "stdout" is a bit confusing. Although
it does make sense for "output" and "input" from the perspective
of the client. But in the context of the new function, it makes
sense to refer to these as their file descriptor names.

In addition, the last use of self._path disappeared, so we stop
setting that attribute and we can delete the redundant URL
parsing necessary to set it.

Differential Revision: https://phab.mercurial-scm.org/D2031

The censor system allows retroactively removing content from
files. Actually censoring a node requires using the censor extension,
but the functionality for handling censored nodes is partially in core.

Censored nodes in a filelog have the flag ``REVIDX_ISCENSORED`` set,
and the contents of the censored node are replaced with a censor
tombstone. For historical reasons, the tombstone is packed in the
filelog metadata field ``censored``. This allows censored nodes to be
(mostly) safely transmitted through old formats like changegroup
versions 1 and 2. When using changegroup formats older than 3, the
receiver is required to re-add the ``REVIDX_ISCENSORED`` flag when
storing the revision. This depends on the ``censored`` metadata key
never being used for anything other than censoring revisions, which is
true as of January 2017. Note that the revlog flag is the
authoritative marker of a censored node: the tombstone should only be
consulted when looking for a reason a node was censored or when revlog
flags are unavailable as mentioned above.

The tombstone data is a free-form string. It's expected that users of
censor will want to record the reason for censoring a node in the
tombstone. Censored nodes must be able to fit in the size of the
content being censored.