If Phabricator is used to import a Mercurial repository which has the blackbox extension enabled, the import will never complete, and the revision log at https://example.com/diffusion/HG/ will show an extra revision at the top, "rHGwarning: cannot write to blackbox.log: Permission denied"; clicking the link results in a HTTP 404 error.
The blackbox extention, documented at https://mercurial.selenic.com/wiki/BlackboxExtension creates a log of operations into .hg/blackbox.log .
Why are you interested in running this extension?
In particular, Phabricator already records all write operations in the repository "Push Log", so repository state is completely reconstructable across force pushes, ref changes, etc.
It's unclear why you would want to log reads made by Phabricator. There will be a huge volume of these events on an active server, and I don't see how they could ever be useful.
The erroneous revision is because when hg log is invoked with --debug, it prints arbitrary messages to stdout which we can not distinguish from log output.
We must use --debug on Mercurial versions older than 2.4 (basically, prior to my June 2012 Mercurial patch, see T5554#133984) because there is no way to obtain full commit hashes from the log output otherwise.
We filter specific well-known messages in PhabricatorRepository::filterMercurialDebugOutput() but can not possibly blacklist every message every extension may emit.
This is an external repository where we want to record push operations done via ssh. We're currently only using Phabricator for the repo browser feature.
Yup, I understand now: we enable the extension system-wide, so I'll update the hgrc in Phabricator's clone of the repo with "blackbox = !" to disable it.
Since I have a workaround should I close this? Or, since my system's using Mercurial 3.5.1 should the code be skipping the workaround for older versions?
Cool, that sounds reasonable. Broadly: