view mercurial/help/internals/censor.txt @ 35412:b1959391a088

extdata: abort if external command exits with non-zero status (BC)

Per the last discussion, this is more reliable and consistent way than
suppressing an error. For grep, erroring out might be inconvenient, but
for curl, non-zero exit status should be detected. The latter wouldn't be
possible if non-zero status is ignored.

https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-October/105727.html

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.