Git is a fantastic method of doing version control of your code. Whether it’s to share with collaborators, or just for your own reference, it almost acts as an absolute point of reference for a wide variety of applications and needs. The basic concept of git is that you have your own folder (in which you edit your code, etc.) and you commit/push those changes to a git repository. Note that Git is a version control SYSTEM and GitHub/BitBucket etc. are services that host repositories using Git as its backend!
The basic procedure of git can be summarised to:
1. Change/add/delete files in your current working directory as necessary. This is followed by a
git add or
git rm command.
2. “Commit” those changes; we usually put a message reflecting the change from step 1. e.g.
git commit -m "I changed this file because it had a bug before."
3. You “push” those changes with
git push to a git repository (e.g. hosted by BitBucket, GitHub, etc.); this is sort of like saying “save” that change.
Typically we use services like GitHub to HOST a repository. We then push our changes to that repository (or
git pull from it) and all is good. However, a powerful concept to bear in mind is the ‘bare’ git repository. This is especially useful if you have code that’s private and should be strictly kept within your company/institution’s server, yet you don’t want people messing about too much with the master version of the code. The diagram below makes the bare git repository concept quite clear:
Let’s start with the easy stuff first. Every git repository (e.g. the one you’re working on in your machine) is a WORKING/NON-BARE git repository. This shows files in your code as you expect it, e.g. *.py or *.c files, etc. A BARE repository is a folder hosted by a server which only holds git OBJECTS. In it, you’ll never see a single .py or .c file, but a bunch of folders and text files that look nothing like your code. By the magic of git, this is easily translated as .py or .c files (basically a version of the working repo) when you
git clone it. Since the bare repo doesn’t contain any of the actual code, you can safely assume that no one can really mess up with the master version without having gone through the process of
git add/commit/push, making everything documented. To start a bare repo…
# Start up a bare repository in a server user@server:$~ git init --bare name_to_repo.git # Go back to your machine then clone it user@machine:$~ git clone user@server:/path/to/repo/name_to_repo.git . # This will clone a empty git repo in your machine cd name_to_repo ls # Nothing should come up. touch README echo "Hello world" >> README git add README git commit -m "Adding a README to initialise the bare repo." git push origin master # This pushes to your origin, which is user@server:/path/to/repo/name_to_repo.git
If we check our folders, we will see the following:
user@machine:$~ ls /path/to/repo README # only the readme exists user@server:$~ ls /path/to/repo/name_to_repo.git/ branches/ config description HEAD hooks/ info/ objects/ refs/
Magic! README isn’t in our git repo. Again, this is because the git repo is BARE and so the file we pushed won’t exist. But when we clone it in a different machine…
user@machine2:$~ git clone user@server:/path/to/repo/name_to_repo.git . ls name_to_repo.git/ README cat README Hello world #magic!
This was a bit of a lightning tour but hopefully you can see that the purpose of a bare repo is to allow you to host code as a “master version” without having you worry that people will see the contents directly til they do a git clone. Once they clone, and push changes, everything will be documented via git, so you’ll know exactly what’s going on!