The testing watch is a cronjob set up by the Release Team <email@example.com> which periodically (currently once a day) mails out summaries of changes to Debian's testing distribution. It gets its data from comparing Sources.gz files directly on ftp-master. (If you are curious, you may look at the code behind the testing watch in our tools git repository at Alioth.)
All emails from the testing watch can be recognized mechanically by having one or more X-Testing-Watch-<foo> headers. (This holds for now, but may change in the future if the script gets integrated with DAK/katie).
Whenever the status of a source package changes, an email will be sent to the maintainer (through firstname.lastname@example.org) with Bcc to the package's PTS subscribers (under keyword summary).
This mail has a X-Testing-Watch-Package header indicating
the source package, and a X-Testing-Watch-Version
whose value is the new version of the package in testing — or
(not in testing) if it was removed.
Daily summaries are sent to debian-testing-changes listing all of the day's migrations. A separate summary of removals will be sent on days where any package is removed from testing.
These summaries have a X-Testing-Watch-Summary header whose content is either migrated or removed.
The software was initially written by Henning Makholm.