kbuild: deb-pkg: remove support for "name <email>" form for DEBEMAIL

Commit d5940c60 ("kbuild: deb-pkg improve maintainer address
generation") supported the "name <email>" form for DEBEMAIL, with
behavior slightly different from devscripts.

In Kbuild, if DEBEMAIL is given in the form "name <email>", it is used
as-is, and DEBFULLNAME is ignored.

In contrast, debchange takes the name from DEBFULLNAME (or NAME) if set,
as described in 'man debchange':

  If this variable has the form "name <email>", then the maintainer name
  will also be taken from here if neither DEBFULLNAME nor NAME is set.

This commit removes support for the "name <email> form for DEBEMAIL,
as the current behavior is already different from debchange, and the
Debian manual suggests setting the email address and name separately in
DEBEMAIL and DEBFULLNAME. [1]

If there are any complaints about this removal, we can re-add it,
with better alignment with the debchange implementation. [2]

[1]: https://www.debian.org/doc/manuals/debmake-doc/ch03.en.html#email-setup
[2]: https://salsa.debian.org/debian/devscripts/-/blob/v2.23.7/scripts/debchange.pl#L802Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

scripts/package/mkdebian

@@ -125,21 +125,15 @@ gen_source ()
 rm -rf debian
 mkdir debian
 
-email=${DEBEMAIL}
-
-# use email string directly if it contains <email>
-if echo "${email}" | grep -q '<.*>'; then
-	maintainer=${email}
+user=${KBUILD_BUILD_USER-$(id -nu)}
+name=${DEBFULLNAME-${user}}
+if [ "${DEBEMAIL:+set}" ]; then
+	email=${DEBEMAIL}
 else
-	# or construct the maintainer string
-	user=${KBUILD_BUILD_USER-$(id -nu)}
-	name=${DEBFULLNAME-${user}}
-	if [ -z "${email}" ]; then
-		buildhost=${KBUILD_BUILD_HOST-$(hostname -f 2>/dev/null || hostname)}
-		email="${user}@${buildhost}"
-	fi
-	maintainer="${name} <${email}>"
+	buildhost=${KBUILD_BUILD_HOST-$(hostname -f 2>/dev/null || hostname)}
+	email="${user}@${buildhost}"
 fi
+maintainer="${name} <${email}>"
 
 if [ "$1" = --need-source ]; then
 	gen_source