Make symlinks relative to their location

src/Rocketeer/Traits/BashModules/Filesystem.php

@@ -55,7 +55,7 @@ public function symlink($folder, $symlink)
 
         // Switch to relative if required
         if ($this->rocketeer->getOption('remote.symlink') === 'relative') {
-            $folder = str_ireplace($this->paths->getFolder(''), '', $folder);
+            $folder = $this->getRelativePath($symlink, $folder);
         }
 
         switch ($this->environment->getOperatingSystem()) {
@@ -292,4 +292,88 @@ protected function fromTo($command, $from, $to)
 
         return $this->run(sprintf('%s %s %s', $command, $from, $to));
     }
+
+    /**
+     * Get a relative path from one file or directory to another.
+     *
+     * If $from is a path to a file (i.e. does not end with a "/"), the
+     * returned path will be relative to its parent directory.
+     *
+     * @param string $from
+     * @param string $to
+     *
+     * @return string
+     */
+    protected function getRelativePath($from, $to)
+    {
+        $from = $this->explodePath($from);
+        $to   = $this->explodePath($to);
+
+        $result = [];
+        $i      = 0;
+
+        // Skip the common path prefix
+        while ($i < count($from) && $i < count($to) && $from[$i] === $to[$i]) {
+            $i++;
+        }
+
+        // Add ".." for each directory left in $from
+        $from_length = count($from) - 1; // Path length without the filename
+        if ($i > 0 && $i < $from_length) {
+            $result = array_fill(0, $from_length - $i, '..');
+        }
+
+        // Add the remaining $to path
+        $result = array_merge($result, array_slice($to, $i));
+
+        return implode('/', $result);
+    }
+
+    /**
+     * Explode the given path into components, resolving any
+     * ".." components and ignoring "." and double separators.
+     *
+     * If the path starts at root directory, the first component
+     * will be empty.
+     *
+     * @param string $path
+     * @param string $separator Path separator to use, defaults to /.
+     *
+     * @return array
+     */
+    protected function explodePath($path, $separator = '/')
+    {
+        $result = [];
+
+        if (strpos($path, $separator) === 0) {
+            // Add empty component if the path starts at root directory
+            $result[] = '';
+        }
+
+        foreach (explode($separator, $path) as $component) {
+            switch ($component) {
+                case '..':
+                    // ".." removes the preceding component
+                    if (empty($result) || $result[count($result) - 1] === '..') {
+                        // Unless the path contains only ".." so far (then keep the "..")
+                        $result[] = '..';
+                        break;
+                    }
+                    if (count($result) === 1 && $result[0] === '') {
+                        // Or the path is already at root (then just ignore it)
+                        break;
+                    }
+                    array_pop($result);
+                    break;
+                case '.':
+                case '':
+                    // Ignore double separators and "."
+                    break;
+                default:
+                    $result[] = $component;
+            }
+        }
+
+        return $result;
+    }
 }