I designed the 3.0 source package format as an extensible format.
This means that the names and extensions of files in the source format
should not be anticipated by parsers, as new file extensions can be added
at any time.

Like these:

Files:
 276249420ea676d779458593f9d0aa00 388859 debhelper_7.9.4.git
 1749401afb14b5a62ae82bcb3fd564ed 738 debhelper_7.9.4.gitshallow

mini-dinstall's current behavior when fed such a .dsc and .changes
is to silently ignore both the above files while installing the rest of
the files.

It seems to look for known source filename extensions only in order to
determine if the upload is a sourceful upload. Seems to me there are two
other ways to do that. One is to look for "Architecture: source" in the
changes file, and the other is to look for a .dsc file in the Files list
of the changes file.

Suggest either of those approaches be used, and unknown file extensions
not be silently skipped, but instead, silently installed.