Fixed Commit::getLastModification

If we use gitlib (located in /a/b/gitlib) and try to inspect a
project located in /a/b ; Gitlib will not be able to get the log
since it run a command like:

    git log --working-dir /a/b/.git --working-tree /a/b log --format=%H -n 1 THEHASH -- PATH

so PATH does not exist in /a/b/gitlib/ (ie /a/b/gitlib/PATH).
so the command fails.

So i fixed it by preprend the working-dir.

Note: I think we should update all commands that use a path in arguments.

ping @alexandresalome

Author: lyrixx

src/Gitonomy/Git/Commit.php

@@ -260,10 +260,11 @@ public function getTree()
      */
     public function getLastModification($path)
     {
-        if (preg_match('#^/#', $path)) {
+        if (0 === strpos($path, '/')) {
             $path = StringHelper::substr($path, 1);
         }
 
+        $path = $this->repository->getWorkingDir().'/'.$path;
         $result = $this->repository->run('log', array('--format=%H', '-n', 1, $this->hash, '--', $path));
 
         return $this->repository->getCommit(trim($result));