Automating Git With Python

September 16, 2020

Programmers are lazy! This is why I wrote a Python script to write one command instead of three in my Git workflow.

Context

This website is made with the static site generator Hugo. Once the layout and theme of the site are chosen, all I needed then was writing new posts. This is done by writing Markdown documents. I also have it version-controlled so that I can host it on Netlify through the GitHub repo.

So this is what happens with the repo after writing every new post:

git add . (it’s only one new file added to the repo)
git commit -m "my commit message"
git push

It is a repetitive task, and it is exactly the same except for the commit message. Sounds like a perfect candidate for an automation script! (Also, a fun Python exercise.)

The code

Here’s the whole script:

#! /usr/bin/python3
from git import Repo, GitCommandError
import sys

if len(sys.argv) < 2:
    print("No message given... exiting")
    sys.exit()
else:
    commit_msg = sys.argv[1]

repo = Repo(".")
repo.git.add("--all")

try:
    repo.git.commit("-m", commit_msg)
    print(f"Successfully added commit: \"{commit_msg}\"")
except GitCommandError:
    print("Nothing to commit... exiting")
    sys.exit()

try:
    origin = repo.remote()
    origin.pull()
    print("Successfully pulled!")
    origin.push()
    print("Successfully pushed!")
except:
    print("Problem with pushing... exiting")
    sys.exit()

If you know a bit of Python and Git, you can very easily understand it. It could have been more complicated to work in more use cases, but I did what would help me with the exact repetition mentioned above.

The script is meant to be executed from the (Linux) shell, where I normally run the Git commands, and takes the commit message as an argument:

./the_script.py "my commit message"

Guards

I have put in some defensive code to avoid crashes or bad commits:

Checking for the commit message argument so that the script exits if I forget to add the message to the execution command.
Handling the exception that is raised when there is nothing to commit. This way the scripts prints a simple message instead of a Python traceback.
Similar behavior with pushing.

Assumptions

The script is far from perfect and, like I said, more can be done. But it works for my specific use case:

The repo and its remote are already set up.
It commits all files (which is almost always one in my case).
It doesn’t care about branches (I commit to and push the master branch).

Repos

I have this script, and a similar one written in R on GitHub:

That’s it! The idea is really simple but kinda cool. I am glad I was able to write a script like this in an hour and have a Python workout in the process. Now, I can update my website with one single command after writing this post and the next ones!

Edit: I added a git pull command to the code. While my workflow so far has the code only going in one direction, pulling is best practice. Thanks to David Kun for the suggestion.

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