fix: parse options ending with 3+ hyphens (#434)

Before this commit, options ending with three or more hyphens were
being parsed as positional arguments, because a regular expression
didn't have a start anchor.

Co-authored-by: Benjamin E. Coe <bencoe@google.com>

lib/yargs-parser.ts

@@ -225,7 +225,7 @@ export class YargsParser {
       if (arg !== '--' && isUnknownOptionAsArg(arg)) {
         pushPositional(arg)
       // ---, ---=, ----, etc,
-      } else if (truncatedArg.match(/---+(=|$)/)) {
+      } else if (truncatedArg.match(/^---+(=|$)/)) {
         // options without key name are invalid.
         pushPositional(arg)
         continue

test/yargs-parser.cjs

@@ -3588,6 +3588,13 @@ describe('yargs-parser', function () {
       args.bar.should.equal('--goodnight moon')
     })
 
+    // see: https://github.com/yargs/yargs-parser/issues/433
+    it('handles strings with three or more trailing dashes', function () {
+      const args = parser('--foo "hello---" --bar="world---"')
+      args.foo.should.equal('hello---')
+      args.bar.should.equal('world---')
+    })
+
     it('respects inner quotes (string)', function () {
       const args = parser('cmd --foo ""Hello"" --bar ""World"" --baz="":)""')
       args.foo.should.equal('"Hello"')