[Baypiggies] Please update baypggies.net / 28-Jan / Explore Git internals using Python / Let's write "git log" in Python

Glen Jarvis glen at glenjarvis.com
Fri Jan 15 01:22:34 EST 2016

I saw no -1 votes for me stepping up to the plate and corralling cats for
our next MeetUp. I even saw a +1, w00t I'm in the black. :)

Please update BayPIGgies.net:

Who: Glen Jarvis
What: Explore Git internals using Python | Let's write "git log" in Python
When: Thursday, January 28, 2016 7:30 PM
Where: LinkedIn Corporation / Stierlin Ct. / Mountain View / CA / Exact
address and room not yet known
Why: Because we need to know the airspeed of an unladen swallow

Git is a powerful tool for source control. It's often misunderstood and
abused. Under the surface Git is an elegant and simple data structure. When
you don't understand that data structure, you don't really understand Git.
It is flexible enough to give you all the rope that you need to hang
yourself in Git hell. However, if you understand it, metaphorical Gordian
knots seem simple and Git hell doesn't exist.

Python is an elegant programming language heavily influenced by ABC "a
teaching language, a replacement for BASIC...." [1] It's a perfect tool
that looks like pseudo-code but executes. However, even with its
simplicity, it is one of the most powerful programming languages that
exists. It is a perfect language to document and run the Git data structure
as we explore it.

In this talk, we start with a simple explanation of the Git data structure
on disk. We then begin live-coding to read those data structures and
reconstruct a `git log` command for any arbitrary git repository without
using the `git` command [2]. When finished, we should have our own working
command that does the same thing as `git log` for any arbitrary repository,
on any branch. We'll simply start at `HEAD` and work our way down the data

Although it is not *useful* to have a Python version of Git, it is *fun*.
Also, this exploration helps you understand the Git tool on a much deeper
level. When you can program something, you can understand it. And,
understanding Git helps you be a better developer and collaborator.

About the Speaker


Glen Jarvis has been programming Python for over 7 years and has been
programming in different languages for over twenty years. Before that, he
was a highly certified database administrator and has been certified in
Linux/Unix administration by UC-Berkeley.

He has worked for companies such as IBM, UC-Berkeley, Sprint and many
Silicon Valley Start-ups. He has worked in the fields of Databases, Data
Science, Bioinformatics and Web Technologies.

Glen has been working for two years at RepairPal, a very successful
start-up that gives you free estimates for what your car repair *should*
cost [3]. He is currently putting the "Dev" in "DevOps" using Ansible (and

He additionally owns a consulting and training company, Glen Jarvis, LLC,
that mentors budding programmers. Some of his training Videos include How
to create a free AWS instance, Ansible Hands-On Training, and An
introduction to Test Driven Development. He has also been an open source
contributor [4].


[2] With one small caveat. There is only one plumbing command used to read
a binary file `git cat-file`. The rest is ASCII text that we can

[3] http://repairpal.com/

[4] https://github.com/glenjarvis/

Also, note that I have cross-posted this on my own company's MeetUp site.
Although this is not the BayPIGgies site, the more people that we see RSVP
here, the more newcomers will be interested in attending (no one likes
being the first one at a party):

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