util: split getopt error handling into utility function

esv.d

@@ -20,7 +20,6 @@
 
 module esv;
 
-import std.algorithm : startsWith;
 import std.conv    : to, ConvException;
 import std.file    : exists, mkdirRecurse, write, FileException;
 import std.format  : format;
@@ -76,14 +75,7 @@ main(string[] args)
 			"V", &VFlag,
 		);
 	} catch (GetOptException e) {
-		string opt = extractFlag(e);
+		handleOptError(e.msg);
-
-		enforceDie(!e.msg.startsWith("Unrecognized option"),
-			"unknown option " ~ opt);
-		enforceDie(!e.msg.startsWith("Missing value for argument"),
-			"missing argument for option " ~ opt);
-
-		die(e.msg); /* catch-all */
 	}
 
 	if (VFlag) {

util.d

@@ -1,7 +1,6 @@
 module util;
 
-import std.getopt : GetOptException;
+import std.stdio : File;
-import std.stdio  : File;
 
 public @safe:
 
@@ -42,12 +41,20 @@ enforceDie(A...)(bool cond, string fmt, A a)
 		die(format(fmt, a));
 }
 
-string
+void
-extractFlag(in GetOptException e)
+handleOptError(in string msg)
 {
+	import std.algorithm : startsWith;
 	import std.regex : matchFirst;
 
-	return e.msg.matchFirst("-.")[0];
+	string opt = msg.matchFirst("-.")[0];
+
+	enforceDie(!msg.startsWith("Unrecognized option"),
+		"unknown option " ~ opt);
+	enforceDie(!msg.startsWith("Missing value for argument"),
+		"missing argument for option " ~ opt);
+
+	die(msg); /* catch-all */
 }
 
 string