The revision control arrangment (branching, etc.) has had to
accommodate both source-level package versioning (i.e. emacs25,
emacs26, ...) and splitting the upstream code into two source packages
-for each release (i.e. emacs and emacs-non-dfsg), but the emacs
+for each release (i.e. emacs and emacs-non-dfsg), though the emacs
packages have been unversioned, so the former doesn't apply right now.
In any case, that's why all the refs include the source package name.
The refs are prefixed with deb/ to support packaging work in a
repository that might also be used for normal upstream development
-(say you're in both roles) so conflicts will be unlikely.
+(say you're in both roles), such that conflicts will be unlikely.
Finally, the refs include the release name to ease/normalize work
across releases, backports, etc.