Merge branch 'pr/19'

IO-483: getPrefixLength return -1 if unix file contains colon

This closes #19

Thanks to @marko-vasic

Author: kinow

src/main/java/org/apache/commons/io/FilenameUtils.java

@@ -666,6 +666,8 @@ public static int getPrefixLength(final String filename) {
                         return 2;
                     }
                     return 3;
+                } else if (ch0 == UNIX_SEPARATOR) {
+                    return 1;
                 }
                 return NOT_FOUND;
 

src/test/java/org/apache/commons/io/FilenameUtilsTestCase.java

@@ -570,6 +570,10 @@ public void testGetPrefixLength() {
         assertEquals(9, FilenameUtils.getPrefixLength("//server/a/b/c.txt"));
         assertEquals(-1, FilenameUtils.getPrefixLength("\\\\\\a\\b\\c.txt"));
         assertEquals(-1, FilenameUtils.getPrefixLength("///a/b/c.txt"));
+
+        assertEquals(1, FilenameUtils.getPrefixLength("/:foo"));
+        assertEquals(1, FilenameUtils.getPrefixLength("/:/"));
+        assertEquals(1, FilenameUtils.getPrefixLength("/:::::::.txt"));
     }
 
     @Test