CommandLineOptions: allow open-ended quotes in @-files.

We do not enforce an ending quote in @-files
and simply close the string on end-fo-file.
This might be nicer for the user and does not harm.

core/src/main/java/com/google/googlejavaformat/java/CommandLineOptionsParser.java

@@ -45,9 +45,9 @@ final class CommandLineOptionsParser {
    * For simplicity, we do not handle escaped quotes.
    */
   private static final Pattern ARG_MATCHER = Pattern.compile(
-          "\"([^\"]*)\"" + // group 1: string in double quotes, with whitespace allowed
+          "\"([^\"]*)(?:\"|$)" + // group 1: string in double quotes (or until EOF), with whitespace allowed
           "|" + // OR
-          "'([^']*)'" + // group 2: string in single quotes, with whitespace allowed
+          "'([^']*)(?:'|$)" + // group 2: string in single quotes (or until EOF), with whitespace allowed
           "|" + // OR
           "([^\\s\"']+)"  // group 3: unquoted string, without whitespace and without any quotes
   );

core/src/test/java/com/google/googlejavaformat/java/CommandLineOptionsParserTest.java

@@ -226,12 +226,12 @@ public void paramsFileWithQuotesAndWhitespaces() throws IOException {
 
     String[] args = {"--dry-run", "@" + exit, "L +w", "@" + outer, "Q +w"};
 
-    Files.write(exit, "--set-exit-if-changed".getBytes(UTF_8));
+    Files.write(exit, "--set-exit-if-changed 'K +w".getBytes(UTF_8));
     Files.write(outer, ("\"'M' +w\"\n\"@" + nested.toAbsolutePath() + "\"\n'\"P\" +w'").getBytes(UTF_8));
-    Files.write(nested, "\"ℕ +w\"\n\n   \n\"@@O +w\"\n".getBytes(UTF_8));
+    Files.write(nested, "\"ℕ +w\"\n\n   \n\"@@O +w\n".getBytes(UTF_8));
 
     CommandLineOptions options = CommandLineOptionsParser.parse(Arrays.asList(args));
-    assertThat(options.files()).containsExactly("L +w", "'M' +w", "ℕ +w", "@O +w", "\"P\" +w", "Q +w");
+    assertThat(options.files()).containsExactly("K +w", "L +w", "'M' +w", "ℕ +w", "@O +w", "\"P\" +w", "Q +w");
   }
 
   @Test