Add compability to current formalism to short_channel_id-to-txid.sh

* Add compatibility with the new shortchannelid syntax with x as separator

* Add an error message in case the parse failed, instead of receveing an unrelated error from the bitcoin-cli

contrib/short_channel_id-to-txid.sh

@@ -2,14 +2,27 @@
 
 set -e
 
-if [ "$#" != 1 ]; then
-    echo Usage: "$0" "short:channel:id" >&2
+if [ "$#" != 1 ]
+then
+    echo Usage: "$0" "shortchannelid (e.g. 532046x1702x0 or 532046:1702:0)" >&2
     echo Uses bitcoin-cli to extract the actual txid >&2
     exit 1
 fi
 
-BLOCK=$(echo "$1" | cut -d: -f1)
-TXNUM=$(echo "$1" | cut -d: -f2)
+# Try to segment using both x and : as delimiters (compatibility with the old shortchannelid standard)
+BLOCK=$(echo "$1" | cut -dx -f1)
+TXNUM=$(echo "$1" | cut -dx -f2)
 
-bitcoin-cli getblock "$(bitcoin-cli getblockhash "$BLOCK")" true | grep '^    "' | head -n "$((TXNUM + 1))" | tail -n 1 | tr -dc '0-9a-f\n'
+if [ "$BLOCK" = "$1" ] && [ "$TXNUM" = "$1" ]
+then
+    BLOCK=$(echo "$1" | cut -d: -f1)
+    TXNUM=$(echo "$1" | cut -d: -f2)
+fi
+
+if [ "$BLOCK" = "$1" ] && [ "$TXNUM" = "$1" ]
+then
+    echo The provided shortchannelid is invalid. Valid examples: 532046x1702x0 or 532046:1702:0 >&2
+    exit 1
+fi
 
+bitcoin-cli getblock "$(bitcoin-cli getblockhash "$BLOCK")" true | grep '^    "' | head -n "$((TXNUM + 1))" | tail -n 1 | tr -dc '0-9a-f\n'