Ignoring Things

Overview

Teaching: 5 min
Exercises: 0 min

Questions

• How can I tell Git to ignore files I don’t want to track?

Objectives

• Configure Git to ignore specific files.

• Explain why ignoring files can be useful.

This section will touch briefly on how you can tell git to ignore certain files and why that can be useful.

What if we have files that we do not want Git to track for us, like backup files created by our editor or intermediate files created during data analysis.

CLI Steps

We do this by creating a file in the root directory of our project called .gitignore:

$ nano .gitignore
$ cat .gitignore

.DS_Store

These patterns tell Git to ignore any file whose name is .DS_Store (a common hidden file created on macOS).

Once we have created this file, we can add it to repository so that we never even see these distracting files.

$ git status

On branch master
Untracked files:
  (use "git add <file>..." to include in what will be committed)

	.gitignore

nothing added to commit but untracked files present (use "git add" to track)

You might think we wouldn’t want to track the .gitignore file, but everyone we’re sharing our repository with will probably want to ignore the same things that we’re ignoring. Let’s add and commit .gitignore:

$ git add .gitignore
$ git commit -m "Ignore .DS_Store files."
$ git status

To ignore files in your repository with GitHub Desktop go to the Repository menu and select Repository Settings…

With the Repository Settings pop-up open, click the Ignored Files tab. Here you will be able to add file names, directory names, or patterns for Git to ignore in your repository.

If you want to follow along, add .DS_Store to the list, which a common macOS hidden system file that often is accidentally added to repositories.

You will notice a new change has been staged for the repository because the Git ignore file did not exist before. The hidden .gitignore file is how Git tracks which files to not track. You’ll need to add it to the repository to make sure you continually ignore those files.

This is as much as we’ll cover in this section, but take a look at the tips below if you want more information.

Ignoring Nested Files

Given a directory structure that looks like:

results/data
results/plots

How would you ignore only results/plots and not results/data?

Solution

As with most programming issues, there are a few ways that you could solve this. If you only want to ignore the contents of results/plots, you can change your .gitignore to ignore only the /plots/ subfolder by adding the following line to your .gitignore:

results/plots/

If, instead, you want to ignore everything in /results/, but wanted to track results/data, then you can add results/ to your .gitignore and create an exception for the results/data/ folder. The next challenge will cover this type of solution.

Sometimes the ** pattern comes in handy, too, which matches multiple directory levels. E.g. **/results/plots/* would make git ignore the results/plots directory in any root directory.

Including Specific Files

How would you ignore all .data files in your root directory except for final.data? Hint: Find out what ! (the exclamation point operator) does

Solution

You would add the following two lines to your .gitignore:

*.data           # ignore all data files
!final.data      # except final.data

The exclamation point operator will include a previously excluded entry.

Ignoring all data Files in a Directory

Given a directory structure that looks like:

results/data/position/gps/a.data
results/data/position/gps/b.data
results/data/position/gps/c.data
results/data/position/gps/info.txt
results/plots

What’s the shortest .gitignore rule you could write to ignore all .data files in result/data/position/gps? Do not ignore the info.txt.

Solution

Appending results/data/position/gps/*.data will match every file in results/data/position/gps that ends with .data. The file results/data/position/gps/info.txt will not be ignored.

The Order of Rules

Given a .gitignore file with the following contents:

*.data
!*.data

What will be the result?

Solution

The ! modifier will negate an entry from a previously defined ignore pattern. Because the !*.data entry negates all of the previous .data files in the .gitignore, none of them will be ignored, and all .data files will be tracked.

Log Files

You wrote a script that creates many intermediate log-files of the form log_01, log_02, log_03, etc. You want to keep them but you do not want to track them through git.

1. Write one .gitignore entry that excludes files of the form log_01, log_02, etc.

2. Test your “ignore pattern” by creating some dummy files of the form log_01, etc.

3. You find that the file log_01 is very important after all, add it to the tracked files without changing the .gitignore again.

4. Discuss with your neighbor what other types of files could reside in your directory that you do not want to track and thus would exclude via .gitignore.

Solution

1. append either log_* or log* as a new entry in your .gitignore
2. track log_01 using git add -f log_01

Key Points

• The .gitignore file tells Git what files to ignore.