Git clone now gets the right branch from the getgo

Simplified the instructions by two steps.

doc/install/installation.md

@@ -144,13 +144,10 @@ GitLab Shell is an ssh access and repository management software developed speci
     cd /home/git
     # Clone gitlab shell
-    sudo -u git -H git clone https://github.com/gitlabhq/gitlab-shell.git
+    sudo -u git -H git clone https://github.com/gitlabhq/gitlab-shell.git -b v1.7.9
     cd gitlab-shell
-    # switch to right version
-    sudo -u git -H git checkout v1.7.9
-
     sudo -u git -H cp config.yml.example config.yml
     # Edit config and replace gitlab_url
@@ -174,14 +171,11 @@ To setup the MySQL/PostgreSQL database and dependencies please see [`doc/install
 ## Clone the Source
     # Clone GitLab repository
-    sudo -u git -H git clone https://github.com/gitlabhq/gitlabhq.git gitlab
+    sudo -u git -H git clone https://github.com/gitlabhq/gitlabhq.git -b 6-3-stable gitlab
     # Go to gitlab dir
     cd /home/git/gitlab
-    # Checkout to stable release
-    sudo -u git -H git checkout 6-3-stable
-
 **Note:**
 You can change `6-3-stable` to `master` if you want the *bleeding edge* version, but never install master on a production server!