How does one include the original upstream signature?

[Theodore Ts'o <tytso@mit.edu>]

I'm getting the following lintian error message:

E: e2fsprogs changes: orig-tarball-missing-upstream-signature e2fsprogs_1.43.5.orig.tar.gz
N:
N:    The packaging includes an upstream signing key but the corresponding
N:    .asc signature for one or more source tarballs are not included in your
N:    .changes file.
N:
N:    Severity: important, Certainty: certain
N:
N:    Check: changes-file, Type: changes
N:

... but I can't figure out how to get the changes file to include the
original upstream signature file.  I've tried naming the upstream
signature file e2fsprogs_1.43.5.orig.tar.gz.asc; I've tried naming it
e2fsprogs-1.43.5.tar.gz.  Neither cause dpkg-buildpackage to include
the signature file.

I've checked the man pages for dpkg-source, dpkg-genchanges, and
dpkg-buildpackage; none shed any light on the subject.  I've tried
some google searches, and the closest I've come to documentation is:

https://bugs.debian.org/cgi-bin/bugreport.cgi?att=1;bug=833585;filename=0001-Check-for-the-presence-of-a-signature-if-an-upstream.patch;msg=12

...but I don't understand the internals of Lintian enough to figure
out what filename it is looking for.

Further google searches seem to indicate the only way I can get
Lintian to shut up is to delete debian/upstream/signing-key.asc.
Which I will do if I have to, since debian-watch really isn't all that
interesting when I'm the upstream.  But I can't help thinking that
either some documentation is sorely lacking; the Lintian information
is needs more information; or I've missed something basic.  Or perhaps
all three or some combination of all three.

Help me, debian-devel!  You're my only hope!

					- Ted