If revisions 1-130 exist, it errors at "svn log -r 1:250", so we can't
reliably give a last number. Easiest solution is to just forego per-batch
processing, and fetch all the unseen entries in one go.
It isn't triggered by anything yet. When the observer is called, it uses
Blinker to send out a signal for every [T12345] marker it sees in the
first line of each commit log. Those signals aren't connected to anything
yet.
NOTE: this requires the 'svn' Python module , which is a wrapper for the
'svn' commandline client. This client needs to be installed on our docker
when we deploy.
