Mauro Bringolf

Currently geeking out as WordPress developer at WebKinder and student of computer science at ETH.

Let’s learn Git: Logs and Diffs

September 10, 2017
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This is the second post in a series of notes on version control with Git. The first article is about undoing or fixing the most recent commit in a Git repository. We will take a step back for the second article and cover various flavors of two basic commands that help us inspect the current state of a repository: log and diff. All of the presented commands only read and present Git data without making any changes to the repository and can therefore be safely played around with.

Logs: Inspecting history

A Git repository stores history of a project by creating a sequence of snapshots called commits. It also allows for multiple concurrent tracks of different histories called branches. Branches can share history, diverge and join at different points. As a whole, the history of a repository is a graph of commits. But sometimes we get lost and need a map. With git log we can get a list of the commits on the current branch and see where we currently are. The list is in reverse chronological order showing the most recent commit on top going down all the way to the oldest. There are a couple of helpful arguments and options to this command. Just like with any other Git command, there are many more options but these are the ones that have helped me the most so far. They can all be combined to create precisely tailored logs.

Diffs: Viewing changes

Logging examples using the semver project

In order to run a few examples we need a Git repository. It does not matter which one as long as there is enough history in it, so I chose semver, the semantic versioning specification 1. You should not be able to break anything by running any of these commands, so I recommend you use a repository of your own. Let’s go:

This is a screenshot of my terminal so please excuse the ugly styling. This example combines three options to get an overview of what files were changed in the last five commits.

Here the form with a start and end commit is used. Instead of specifying the range with SHA hashes it uses tag names which point to a certain commit. Therefore this log shows all commits that happened between release candidate 1 and the actual release of version 1.0.0.

References

  1. https://github.com/mojombo/semver