Add grep_dd_sigs script

grep_dd_sigs gives the list of DD which have signed a key with their DD
key (the key they have in the Debian keyring).

debian/README

@@ -0,0 +1,9 @@
+grep_dd_sigs is meant to extract the list of all signature from a given
+key, made by keys from the Debian Developer keyring.
+
+To install this script, just copy it in a directory which is in the
+PATH, e.g. /usr/local/bin:
+  cp grep_dd_sigs /usr/local/bin
+
+Usage:
+	grep_dd_sigs $keyid

debian/grep_dd_sigs

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+sigs=$(gpg --with-colons --check-sigs $1 \
+	| grep "sig:\!" \
+	| sed -r "s/sig:\!::[[:digit:]]+:([[:alnum:]]+):.*$/\1/")
+
+echo $sigs | while read key
+	do
+		gpg --no-default-keyring --keyring /usr/share/keyrings/debian-keyring.gpg --list-keys $key 2>/dev/null \
+			| grep "debian.org" \
+			| grep "^uid" \
+			| sed -r "s/^uid +//" \
+			| sort -d \
+			| uniq
+	done