Home | Posts by Category

Visualize changes to the Git DAG in real-time

Teaching users how to perform more than just the basic Git operations eventually requires some discussion about the Git DAG. It’s the the inevitable just think of branches as… discussion and while that has become something of an overused joke, it really is a useful and effective mental model.

Git users that only use the push, pull, merge, and commit commands are often worried about “messing up” a repository by using the “destructive” commands and never venture deeper. Doing so is well worth the effort though! Git is something all developers use day-in and day-out, investing a handful of hours in a Git training will pay time dividends in the years to come, and increases a developer’s confidence when crafting a PR. I often highly recommend spending a weekend with the Pro Git book, by Scott Chacon and going through the examples.

When I run Git training sessions, I lean heavily on a shell script that uses Graphviz to draw a graphical representation of the actual Git DAG (originally adapted from an example in the (now deprecated) Git Wiki). With a tiny bit of helper machinery it can even display changes in (near) real-time:

(The git stub command can be a simple alias around touch A; git add A; git commit -m "Add-A" to quickly stub out new Git commits when running training workshops.)

The “magic” of the script is using the reference-transaction Git hook to regenerate the graph whenever a reference changes, plus any image viewer that will update the display when the underlying file changes. The excellent ImageMagick ships with one that works beautifully on Linux, Windows with WSL2 (since X11 works out-of-box nowadays with WSL2!), and OS X with XQuartz – also untested, but I think Preview.app may work as well.

If you’re interested in using it when running your own Git trainings, or just playing around on your own, you can pull the script out of my dotfiles repository. Just put it somewhere on your $PATH. I may extract it into a separate repo if there’s interest.