feature: Added GPG long keyid support

Now, user input of a key is validated to see if it's 8 or 16 chars.
If it's 8 chars, it's assumed to be a short id, if 16 it's long.

From there the key ID matched against that in the local datastore.

TODO.md

@@ -6,7 +6,6 @@ Below is a rough list of things to be resolved
   * Improve in memory handling
   * Improve filename handling
   * Support Trust levels
-  * Add full public key id handling (the short id is only 8 chars long, even better to utilize the full id)
   * Document exit codes and make them more explicit
 
 ### Bugs

main.go

@@ -210,12 +210,31 @@ func checkGPG(file File) (state SigState, err error) {
 		fmt.Printf("Invalid signature or public key not present: %s\n", err)
 		os.Exit(2)
 	}
-	state.sig = signer.PrimaryKey.KeyIdShortString()
 
-	if len(*flagKeyid) > 0 {
-		keyid := strings.ToUpper(*flagKeyid)
-		if keyid != state.sig {
-			fmt.Printf("The remote file was not signed by the expected GPG Public key. Expected %s and got %s\n", keyid, state.sig)
+	state.sig = signer.PrimaryKey.KeyIdString()
+
+	l := len(*flagKeyid)
+	if l > 0 {
+		var rid string
+
+		// Force the local id to be all uppercase
+		lid := strings.ToUpper(*flagKeyid)
+
+		// check the number of chars on the remote id to see if it's a
+		// short or long id. If it's not 8 or 16, it's not valid.
+		switch l {
+		case 8:
+			rid = signer.PrimaryKey.KeyIdShortString()
+		case 16:
+			rid = signer.PrimaryKey.KeyIdString()
+		}
+		if len(rid) == 0 {
+			fmt.Printf("You did not specify a valid GPG keyid length. Must be 8 or 16 characters.")
+			os.Exit(2)
+		}
+
+		if lid != rid {
+			fmt.Printf("The remote file was not signed by the expected GPG Public key. Expected %s and got %s\n", lid, rid)
 			os.Exit(2)
 		}
 	}