Fixed issue 119, no environment for the shell_exec and exec calls.

For each call exec or shell_exec, I have added the ability to prepend a
string. For example '/usr/bin/env -i '.

src/IDF/Plugin/SyncGit/Serve.php

@@ -191,7 +191,8 @@ class IDF_Plugin_SyncGit_Serve
     public function initRepository($fullpath)
     {
         mkdir($fullpath, 0750, true);
-        exec(sprintf('git --git-dir=%s init', escapeshellarg($fullpath)), 
+        exec(sprintf(Pluf::f('idf_exec_cmd_prefix', '').
+                     'git --git-dir=%s init', escapeshellarg($fullpath)), 
              $out, $res);
         if ($res != 0) {
             throw new Exception(sprintf('Init repository error, exit status %d.', $res));

src/IDF/Plugin/SyncMercurial.php

@@ -79,6 +79,7 @@ class IDF_Plugin_SyncMercurial
         $output = array();
         $cmd = sprintf('hg init %s', 
                        escapeshellarg($mercurial_path.'/'.$shortname));
+        $cmd = Pluf::f('idf_exec_cmd_prefix', '').$cmd;
         $ll = exec($cmd, $output, $return);
         return ($return == 0);
     }

src/IDF/Plugin/SyncSvn.php

@@ -79,6 +79,7 @@ class IDF_Plugin_SyncSvn
         $output = array();
         $cmd = sprintf('svnadmin create %s', 
                        escapeshellarg($svn_path.'/'.$shortname));
+        $cmd = Pluf::f('idf_exec_cmd_prefix', '').$cmd;
         $ll = exec($cmd, $output, $return);
         return ($return == 0);
     }