Update installation instructions for source build (#967)

* Update installation.rst

* Fix git command

(cherry picked from commit 2d5e315)

# Conflicts:
#	ur_robot_driver/doc/installation/installation.rst

ur_robot_driver/doc/installation/installation.rst

@@ -0,0 +1,71 @@
+Installation of the ur_robot_driver
+===================================
+
+You can either install this driver from binary packages as shown above or build it from source. We
+recommend a binary package installation unless you want to join development and submit changes.
+
+Install from binary packages
+----------------------------
+
+1. `Install ROS2 <https://docs.ros.org/en/rolling/Installation/Ubuntu-Install-Debians.html>`_. This
+   branch supports only ROS2 Rolling. For other ROS2 versions, please see the respective branches.
+2. Install the driver using
+
+   .. code-block:: bash
+
+     sudo apt-get install ros-${ROS_DISTRO}-ur
+
+
+Build from source
+-----------------
+
+Before building from source please make sure that you actually need to do that. Building from source
+might require some special treatment, especially when it comes to dependency management.
+Dependencies might change from time to time. Upstream packages (such as the library) might change
+their features / API which require changes in this repo. Therefore, this repo's source builds might
+require upstream repositories to be present in a certain version as otherwise builds might fail.
+Starting from scratch following exactly the steps below should always work, but simply pulling and
+building might fail occasionally.
+
+1. `Install ROS2 <https://docs.ros.org/en/rolling/Installation/Ubuntu-Install-Debians.html>`_. This
+   branch supports only ROS2 Rolling. For other ROS2 versions, please see the respective branches.
+
+   Once installed, please make sure to actually `source ROS2 <https://docs.ros.org/en/rolling/Tutorials/Beginner-CLI-Tools/Configuring-ROS2-Environment.html#source-the-setup-files>`_ before proceeding.
+
+3. Make sure that ``colcon``, its extensions and ``vcs`` are installed:
+
+   .. code-block:: bash
+
+     sudo apt install python3-colcon-common-extensions python3-vcstool
+
+
+4. Create a new ROS2 workspace:
+
+   .. code-block:: bash
+
+     export COLCON_WS=~/workspace/ros_ur_driver
+     mkdir -p $COLCON_WS/src
+
+5. Clone relevant packages (replace ``<branch>`` with ``humble``, ``iron`` or ``main`` for rolling), install dependencies, compile, and source the workspace by using:
+
+   .. code-block:: bash
+
+     cd $COLCON_WS
+     git clone -b <branch> https://github.com/UniversalRobots/Universal_Robots_ROS2_Driver.git src/Universal_Robots_ROS2_Driver
+     vcs import src --skip-existing --input src/Universal_Robots_ROS2_Driver/Universal_Robots_ROS2_Driver-not-released.${ROS_DISTRO}.repos
+     rosdep update
+     rosdep install --ignore-src --from-paths src -y
+     colcon build --cmake-args -DCMAKE_BUILD_TYPE=Release
+     source install/setup.bash
+
+6. When consecutive pulls lead to build errors it is possible that you'll have to build an upstream
+   package from source, as well. See the [detailed build status](ci_status.md). When the binary builds are red, but
+   the semi-binary builds are green, you need to build the upstream dependencies from source. The
+   easiest way to achieve this, is using the repos file:
+
+   .. code-block:: bash
+
+     cd $COLCON_WS
+     vcs import src --skip-existing --input src/Universal_Robots_ROS2_Driver/Universal_Robots_ROS2_Driver.${ROS_DISTRO}.repos
+     rosdep update
+     rosdep install --ignore-src --from-paths src -y