PathTool.getRelativeFilePath: fix broken Windows drive-letter regex

src/main/java/org/apache/maven/shared/utils/PathTool.java

@@ -143,10 +143,16 @@ public static String getRelativeFilePath(final String oldPath, final String newP
         String toPath = new File(newPath).getPath();
 
         // strip any leading slashes if its a windows path
-        if (toPath.matches("^\\[a-zA-Z]:")) {
+        if (toPath.length() > 2
+                && toPath.charAt(0) == '\\'
+                && Character.isLetter(toPath.charAt(1))
+                && toPath.charAt(2) == ':') {
             toPath = toPath.substring(1);
         }
-        if (fromPath.matches("^\\[a-zA-Z]:")) {
+        if (fromPath.length() > 2
+                && fromPath.charAt(0) == '\\'
+                && Character.isLetter(fromPath.charAt(1))
+                && fromPath.charAt(2) == ':') {
             fromPath = fromPath.substring(1);
         }
 

src/test/java/org/apache/maven/shared/utils/PathToolTest.java

@@ -102,6 +102,15 @@ public void testGetRelativePath2Parm() {
         assertEquals("", PathTool.getRelativePath("/usr/local/java/bin/java.sh", "/usr/local/"));
     }
 
+    @Test
+    public void testGetRelativeFilePathWithDifferentWindowsDrives() {
+        // Tests that the regex fix at line 146 correctly strips a leading backslash
+        // before a Windows drive letter. The old regex "^\\[a-zA-Z]:" matched the
+        // literal string "[a-zA-Z]:" instead of a backslash + drive letter.
+        // Different drives with leading backslash should return null.
+        assertNull(PathTool.getRelativeFilePath("\\C:\\usr\\local", "\\D:\\usr\\local\\java\\bin"));
+    }
+
     @Test
     public void testUppercaseDrive() {
         assertNull(PathTool.uppercaseDrive(null));