Fix off-by-one error in Strings.count()

Change-Id: I0667b1624827d1cf0cc1b81f86c7bb44eafd68a7
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

org.eclipse.jgit.test/tst/org/eclipse/jgit/ignore/internal/StringsTest.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2017, Thomas Wolf <thomas.wolf@paranor.ch>
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.eclipse.jgit.ignore.internal;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class StringsTest {
+
+	private void testString(String string, int n, int m) {
+		assertEquals(string, n, Strings.count(string, '/', false));
+		assertEquals(string, m, Strings.count(string, '/', true));
+	}
+
+	@Test
+	public void testCount() {
+		testString("", 0, 0);
+		testString("/", 1, 0);
+		testString("//", 2, 0);
+		testString("///", 3, 1);
+		testString("////", 4, 2);
+		testString("foo", 0, 0);
+		testString("/foo", 1, 0);
+		testString("foo/", 1, 0);
+		testString("/foo/", 2, 0);
+		testString("foo/bar", 1, 1);
+		testString("/foo/bar/", 3, 1);
+		testString("/foo/bar//", 4, 2);
+		testString("/foo//bar/", 4, 2);
+		testString(" /foo/ ", 2, 2);
+	}
+}

org.eclipse.jgit/src/org/eclipse/jgit/ignore/internal/Strings.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2014, Andrey Loskutov <loskutov@gmx.de>
+ * Copyright (C) 2014, 2017 Andrey Loskutov <loskutov@gmx.de>
  * and other copyright owners as documented in the project's IP log.
  *
  * This program and the accompanying materials are made available
@@ -123,12 +123,15 @@ public class Strings {
 	static int count(String s, char c, boolean ignoreFirstLast) {
 		int start = 0;
 		int count = 0;
-		while (true) {
+		int length = s.length();
+		while (start < length) {
 			start = s.indexOf(c, start);
-			if (start == -1)
+			if (start == -1) {
 				break;
-			if (!ignoreFirstLast || (start != 0 && start != s.length()))
+			}
+			if (!ignoreFirstLast || (start != 0 && start != length - 1)) {
 				count++;
+			}
 			start++;
 		}
 		return count;