fix: store flags as ordered

Fixes #78

CHANGELOG.md

@@ -1,5 +1,15 @@
 # Commander Changelog
 
+## Master
+
+### Bug Fixes
+
+- Fixed ordering of flags in the "Unknown Arguments" help output of a command.
+  Flags have previously been stored in an un orderered set and thus upon
+  printing them back out their order was not persisted and a flag part such as
+  `-user` can be printed as `-usre`.
+  [#78](https://github.com/kylef/Commander/issues/78)
+
 ## 0.9.0 (2019-06-12)
 
 ### Breaking

Sources/Commander/ArgumentParser.swift

@@ -6,7 +6,7 @@ private enum Arg : CustomStringConvertible, Equatable {
   case option(String)
 
   /// A flag
-  case flag(Set<Character>)
+  case flag([Character])
 
   var description:String {
     switch self {
@@ -78,8 +78,7 @@ public final class ArgumentParser : ArgumentConvertible, CustomStringConvertible
           let option = flags[flags.index(after: flags.startIndex)..<flags.endIndex]
           return .option(String(option))
         }
-
-        return .flag(Set(flags))
+        return .flag(Array(String(flags)))
       }
 
       return .argument(argument)
@@ -194,7 +193,7 @@ public final class ArgumentParser : ArgumentConvertible, CustomStringConvertible
       case .flag(let option):
         var options = option
         if options.contains(flag) {
-          options.remove(flag)
+          options.removeAll(where: { $0 == flag })
           arguments.remove(at: index)
 
           if !options.isEmpty {

Tests/CommanderTests/ArgumentParserSpec.swift

@@ -151,4 +151,12 @@ let testArgumentParser: ((ContextType) -> Void) = {
       try expect(value2) == "value2"
     }
   }
+
+  $0.describe("#description") {
+    $0.it("should maintain flag ordering") {
+      let parser = ArgumentParser(arguments: ["-user", "-one"])
+
+      try expect(parser.description) == "-user -one"
+    }
+  }
 }