Bug#1023058: git-buildpackage: gbp dch refuses to work with $[DEB]EMAIL unset, doesn't use either at all?

[наб]

Package: git-buildpackage
Version: 0.9.29
Severity: normal

Dear Maintainer,

Every time I do:
-- >8 --
$ gbp dch --verbose -R
gbp:error: Either 'EMAIL' or 'DEBEMAIL' must be set in the environment
for 'dch' to work
-- >8 --
and every time I re-run with EMAIL=: gbp ...

AFAICT, nothing actually uses the variables, so idk why they're
complained about. My config is:
-- >8 --
$ grep -v '^#' ~/.gbp.conf
[DEFAULT]
builder = debuild -i -I -sa
cleaner = fakeroot debian/rules clean
debian-branch = debian
git-debian-branch = debian
git-author = True

[buildpackage]
export-dir = ../build-output/

[import-orig]
dch = False
filter-pristine-tar = True
-- >8 --

The changelog "-- author <mail> date" line correctly lists my public
mailing address (not the machine-local one).

Best,
наб

-- System Information:
Debian Release: bookworm/sid
APT prefers unstable-debug
APT policy: (500, 'unstable-debug'), (500, 'unstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 5.18.0-2-amd64 (SMP w/8 CPU threads; PREEMPT)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages git-buildpackage depends on:
ii devscripts 2.22.2
ii git 1:2.37.2-1
ii man-db 2.11.0-1+b1
ii python3 3.10.6-1
ii python3-dateutil 2.8.2-1
ii python3-pkg-resources 65.5.0-1
ii python3-yaml 5.4.1-1+b2
ii sensible-utils 0.0.17

Versions of packages git-buildpackage recommends:
pn cowbuilder | pbuilder | sbuild <none>
ii pristine-tar 1.49
ii python3-requests 2.27.1+dfsg-1

Versions of packages git-buildpackage suggests:
pn python3-notify2 <none>
ii sudo 1.9.11p3-2
ii unzip 6.0-27

-- no debconf information