add script to generate manpages with help2man

contrib/devtools/gen-manpages.sh

@@ -0,0 +1,18 @@
+#!/bin/sh
+
+# the autodetected version git tag at the end 
+# can screw up manpage output a little bit
+BTCVER=$(bitcoin-cli --version | cut -d"-" -f1 | cut -d"v" -f3)
+
+# Create a footer file with copyright content.
+# This gets autodetected fine for bitcoind if
+# --version-string is not set, but has different
+# outcomes for bitcoin-qt and bitcoin-cli.
+echo "[COPYRIGHT]" > footer.h2m
+bitcoind --version | sed -n '1!p' >> footer.h2m
+
+for cmd in bitcoind bitcoin-qt bitcoin-cli; do
+  help2man -N --version-string=${BTCVER} --include=footer.h2m -o ../../doc/man/${cmd}.1 ${cmd}
+done
+
+rm -f footer.h2m