A research group at your institution wants to incorporate revision control into their project so they can track the user changes made to the code being using.The main software package they use is Mercury.

A high precision integrator for studying the long-term stability of planetary systems, the orbital evolution of comets, asteroids or meteoroids, and simulating planetary accretion.The revision control system they wish to use is Git . as it is employed by their collaborators.They have come to you to write a Git HOWTO using the Linux Git command-line interface and with explicit examples using the Mercury code base. All work on the code will be done on the institution’s Linux HPC, so all user repositories will be local to that machine. They store the“master” code base on their HPC in the directory /home/Mercury/mercury6.

This directory is readable and writeable by the Unix group “mercury”.

All researches using the code are in that group.

The HOWTO needs to cover the following topics:

• A basic description of Git and how it differs from other revision control systems, such as CVS, SVN, darcs, etc.

• A short description of the user’s basic workflow when using a Git repository.

• How to initialise a Git repository for an existing code base. In this case the master code in the directory /home/Mercury/mercury6.

• How to clone an existing master Git repository to a local working repository.

• How to add new files and modified files to the local working Git repository.

• How to recover a particular version of a file from the local Git working repository.

• How to check the status of the local Git repository.

• How to view the change history of the local Git repository.

• How to push local repository changes back to the master Git repository.

• How to pull changes from the master Git repository into the local Git repository.

• Permissions that must be set on the master Git repository so that it can be cloned by users in the research group.

• Permissions that must be set on the users’ local repository so changes can be pushed to the main repository.

Notes:

1. The purpose of every Git command used must be explained.

1. The options used for every Git command must be explained.

1. Every Git command mentioned must show an example of the command using the Mercury code base.

1. Every Git command example must include the command output.

1. The code in the directory /home/Mercury/mercury6 is the Master and all users are pushing their local changes to the master, and pulling other peoples changes from the master to their local copy.

1. The Mercury code is used by the USQ Astronomy group to model the dynamics of Exo-planetary systems. A typical modelling se-quence requires running the code a million times with each run integrating the system forward in time a million years and log if the system is stable or unstable (a planetary collision or ejection).

1. The “git” packages are not installed on the virtual machine, they will need to be installed if you plan to use it to do this question. To install any packages the guest NAT network which connects the guest OS to the Internet through the host’s Internet connection must be brought up. To “bring-up” the NAT interface see the man-pages ifup(8) and interfaces(5)