${DEBFULLNAME-${user}} falls back to ${user} when DEBFULLNAME is unset.
It is more reasonable to do so when DEBFULLNAME is unset or null.
Otherwise, the command:
  $ DEBFULLNAME= make deb-pkg
will leave the name field blank.
The same applies to KBUILD_BUILD_USER and KBUILD_BUILD_HOST.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
 rm -rf debian
 mkdir debian
 
-user=${KBUILD_BUILD_USER-$(id -nu)}
-name=${DEBFULLNAME-${user}}
+user=${KBUILD_BUILD_USER:-$(id -nu)}
+name=${DEBFULLNAME:-${user}}
 if [ "${DEBEMAIL:+set}" ]; then
        email=${DEBEMAIL}
 else
-       buildhost=${KBUILD_BUILD_HOST-$(hostname -f 2>/dev/null || hostname)}
+       buildhost=${KBUILD_BUILD_HOST:-$(hostname -f 2>/dev/null || hostname)}
        email="${user}@${buildhost}"
 fi
 maintainer="${name} <${email}>"