diff --git a/src/IDF/Plugin/SyncGit/Serve.php b/src/IDF/Plugin/SyncGit/Serve.php
index 67f2d8e..42ba320 100644
--- a/src/IDF/Plugin/SyncGit/Serve.php
+++ b/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));
diff --git a/src/IDF/Plugin/SyncMercurial.php b/src/IDF/Plugin/SyncMercurial.php
index 7ebf9f5..2bd8a5a 100644
--- a/src/IDF/Plugin/SyncMercurial.php
+++ b/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);
     }
diff --git a/src/IDF/Plugin/SyncSvn.php b/src/IDF/Plugin/SyncSvn.php
index b3e39d3..aa30bd5 100644
--- a/src/IDF/Plugin/SyncSvn.php
+++ b/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);
     }
diff --git a/src/IDF/Scm.php b/src/IDF/Scm.php
index b03cc07..fcd60c9 100644
--- a/src/IDF/Scm.php
+++ b/src/IDF/Scm.php
@@ -52,6 +52,7 @@ class IDF_Scm
      */
     public static function exec($command, &$output=array(), &$return=0)
     {
+        $command = Pluf::f('idf_exec_cmd_prefix', '').$command;
         $key = md5($command);
         $cache = Pluf_Cache::factory();
         if (null === ($res=$cache->get($key))) {
@@ -74,6 +75,7 @@ class IDF_Scm
      */
     public static function shell_exec($command)
     {
+        $command = Pluf::f('idf_exec_cmd_prefix', '').$command;
         $key = md5($command);
         $cache = Pluf_Cache::factory();
         if (null === ($res=$cache->get($key))) {
diff --git a/src/IDF/Scm/Git.php b/src/IDF/Scm/Git.php
index 4ea1184..ab1f3c4 100644
--- a/src/IDF/Scm/Git.php
+++ b/src/IDF/Scm/Git.php
@@ -235,7 +235,8 @@ class IDF_Scm_Git
      */
     public function getBlob($request_file_info, $dummy=null)
     {
-        return shell_exec(sprintf('GIT_DIR=%s git cat-file blob %s',
+        return shell_exec(sprintf(Pluf::f('idf_exec_cmd_prefix', '').
+                                  'GIT_DIR=%s git cat-file blob %s',
                                   escapeshellarg($this->repo), 
                                   escapeshellarg($request_file_info->hash)));
     }
@@ -410,7 +411,8 @@ class IDF_Scm_Git
      */
     public function getArchiveCommand($commit, $prefix='git-repo-dump/')
     {
-        return sprintf('GIT_DIR=%s git archive --format=zip --prefix=%s %s',
+        return sprintf(Pluf::f('idf_exec_cmd_prefix', '').
+                       'GIT_DIR=%s git archive --format=zip --prefix=%s %s',
                        escapeshellarg($this->repo),
                        escapeshellarg($prefix),
                        escapeshellarg($commit));
diff --git a/src/IDF/Scm/Mercurial.php b/src/IDF/Scm/Mercurial.php
index c059899..5d79a5d 100644
--- a/src/IDF/Scm/Mercurial.php
+++ b/src/IDF/Scm/Mercurial.php
@@ -398,7 +398,8 @@ class IDF_Scm_Mercurial
      */
     public function getArchiveCommand($commit, $prefix='')
     {
-        return sprintf('hg archive --type=zip -R %s -r %s -',
+        return sprintf(Pluf::f('idf_exec_cmd_prefix', '').
+                       'hg archive --type=zip -R %s -r %s -',
                        escapeshellarg($this->repo),
                        escapeshellarg($commit));
     }
diff --git a/src/IDF/Scm/Svn.php b/src/IDF/Scm/Svn.php
index ecdb073..e2f7a61 100644
--- a/src/IDF/Scm/Svn.php
+++ b/src/IDF/Scm/Svn.php
@@ -369,7 +369,7 @@ class IDF_Scm_Svn
      */
     public function getArchiveCommand($commit, $prefix='git-repo-dump/')
     {
-        throw new Exception(('Unsupported feature.'));
+        throw new Exception('Unsupported feature.');
     }
 
 
diff --git a/src/IDF/conf/idf.php-dist b/src/IDF/conf/idf.php-dist
index c9b3288..8aca31f 100644
--- a/src/IDF/conf/idf.php-dist
+++ b/src/IDF/conf/idf.php-dist
@@ -201,4 +201,11 @@ $cfg['allowed_scm'] = array('git' => 'IDF_Scm_Git',
 
 # Extra text files when displaying source
 # $cfg['idf_extra_text_ext'] = 'ext1 ext2 ext3';
+
+# If you can execute the shell commands executed to get info
+# from the scm  with the user of your PHP process but it is 
+# not working from within PHP, this can be due to the environment 
+# variables not being set correctly. Note the trailing space.
+# $cfg['idf_exec_cmd_prefix'] = '/usr/bin/env -i ';
+
 return $cfg;