-Except in the case where upstream releases only tarballs, we do not
-maintain a separate 'upstream' branch (unless you also happen to be
-involved in upstream development). We work with upstream tags rather
-than any branches, except temporary branches used to prepare patches
-for forwarding upstream, for example.
+In this workflow, we specify upstream tags rather than any branches.
+
+Except when (i) upstream releases only tarballs, (ii) we require DFSG
+filtering, or (iii) you also happen to be involved in upstream
+development, we do not maintain any local branch corresponding to
+upstream, except temporary branches used to prepare patches for
+forwarding, and the like.
+
+The idea here is that from Debian's point of view, upstream releases
+are immutable points in history. We want to make sure that we are
+basing our Debian package on a properly identified upstream version,
+rather than some arbitrary commit on some branch. Tags are more
+useful for this.