merged branch jakzal/FilesystemBugFix (PR symfony#3828)

Commits
-------

22e2ad8 [Filesystem] Fixed relative path calculation for end path which is a subdirectory of the start path.
bc93787 [Filesystem] Fixed relative path calculation for paths with various combinations of trailing directory separators.

Discussion
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[Filesystem] Fixed relative path calculation

Bug fix: yes
Feature addition: no
Backwards compatibility break: no
Symfony2 tests pass: yes

src/Symfony/Component/Filesystem/Filesystem.php

@@ -185,7 +185,8 @@ public function makePathRelative($endPath, $startPath)
         }
 
         // Determine how deep the start path is relative to the common path (ie, "web/bundles" = 2 levels)
-        $depth = substr_count(substr($startPath, $offset), DIRECTORY_SEPARATOR) + 1;
+        $diffPath = trim(substr($startPath, $offset), DIRECTORY_SEPARATOR);
+        $depth = strlen($diffPath) > 0 ? substr_count($diffPath, DIRECTORY_SEPARATOR) + 1 : 0;
 
         // Repeated "../" for each level need to reach the common path
         $traverser = str_repeat('../', $depth);

src/Symfony/Component/Filesystem/Tests/FilesystemTest.php

@@ -443,9 +443,12 @@ public function providePathsForMakePathRelative()
     {
         $paths = array(
             array('/var/lib/symfony/src/Symfony/', '/var/lib/symfony/src/Symfony/Component', '../'),
+            array('/var/lib/symfony/src/Symfony/', '/var/lib/symfony/src/Symfony/Component/', '../'),
+            array('/var/lib/symfony/src/Symfony', '/var/lib/symfony/src/Symfony/Component', '../'),
+            array('/var/lib/symfony/src/Symfony', '/var/lib/symfony/src/Symfony/Component/', '../'),
             array('var/lib/symfony/', 'var/lib/symfony/src/Symfony/Component', '../../../'),
             array('/usr/lib/symfony/', '/var/lib/symfony/src/Symfony/Component', '../../../../../../usr/lib/symfony/'),
-            array('/var/lib/symfony/src/Symfony/', '/var/lib/symfony/', '../src/Symfony/'),
+            array('/var/lib/symfony/src/Symfony/', '/var/lib/symfony/', 'src/Symfony/'),
         );
 
         // fix directory separator