diff --git a/README.md b/README.md
index 5fbc099..0a7ab3d 100644
--- a/README.md
+++ b/README.md
@@ -28,11 +28,18 @@ or run the following command:
     php composer.phar require tivie/php-git-log-parser
 
 ## Quick guide
-To parse the current git repository log, you can simply
+To parse a git repository log, you can simply
 
 ```php
+$repositoryPath = '/path_to_your_repo';
+$revision = 'fe4f1105e10a8fedeb0b4f2f8c4ea43bec56a256..'
+
 $parser = new \Tivie\GitLogParser\Parser();
+$parser->setGitDir($repositoryPath);
+$parser->setRevision($revision);
+echo $parser->getCommand();
 $logArray = $parser->parse();
+
 ```
 
 ## License
diff --git a/src/Parser.php b/src/Parser.php
index 49c3401..39cc029 100644
--- a/src/Parser.php
+++ b/src/Parser.php
@@ -60,8 +60,6 @@ public function __construct(Format $format = null, Command $command = null, $rev
         $this->gitDir = __DIR__;
 
         $this->branch = 'HEAD';
-
-        $this->command = ($command) ? $command : $this->buildCommand();
     }
 
     /**
@@ -106,6 +104,8 @@ public function setCommand(Command $command)
      */
     public function getCommand()
     {
+        if (!$this->command) $this->command = $this->buildCommand();
+
         return $this->command;
     }
 
@@ -145,7 +145,7 @@ public function setGitDir($dir, $check = true)
             throw new Exception("Directory $dir does not exist");
         }
         $this->gitDir = $dir;
-        $this->command->chdir($dir);
+        if ($this->command) $this->command->chdir($dir);
         return $this;
     }
 
@@ -164,13 +164,16 @@ public function setBranch($branch)
             throw new InvalidArgumentException('string', 0);
         }
 
-        $oldBranch = $this->branch;
-        $oldArg = $this->command->searchArgument($oldBranch);
-        if (!$oldArg) {
-            throw new Exception("Couldn't change the command to new branch. Was the Command object modified?");
+        if ($this->command) {
+            $oldBranch = $this->branch;
+            $oldArg = $this->command->searchArgument($oldBranch);
+            if (!$oldArg) {
+                throw new Exception("Couldn't change the command to new branch. Was the Command object modified?");
+            }
+
+            $newArg = new Argument($branch);
+            $this->command->replaceArgument($oldArg, $newArg);
         }
-        $newArg = new Argument($branch);
-        $this->command->replaceArgument($oldArg, $newArg);
 
         $this->branch = $branch;
         return $this;
@@ -183,7 +186,8 @@ public function setBranch($branch)
      */
     public function parse()
     {
-        $result = $this->command->run();
+        $command = $this->getCommand();
+        $result = $command->run();
         $log = $result->getStdOut();
 
         $buffer = array();