Ignoring Things

Teaching: 5 min

Objectives

Configure Git to ignore specific files.
Explain why ignoring files can be useful.

Questions

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

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? Let’s create a few dummy files:

$ mkdir pictures
$ touch a.png b.png c.png pictures/cake1.jpg pictures/cake2.jpg

and see what Git says:

$ git status

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

    a.png
    b.png
    c.png
    pictures/

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

Putting these files under version control would be a waste of disk space. What’s worse, having them all listed could distract us from changes that actually matter, so let’s tell Git to ignore them.

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

$ nano .gitignore

Type the text below into the .gitignore file:

*.png
pictures/

Save the file and exit your editor.

Verify that the file contains the files to ignore.

$ cat .gitignore

*.png
pictures/

These patterns tell Git to ignore any file whose name ends in .png and everything in the pictures directory. (If any of these files were already being tracked, Git would continue to track them.)

Once we have created this file, the output of git status is much cleaner:

$ git status

On branch main
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)

The only thing Git notices now is the newly-created .gitignore file. You might think we wouldn’t want to track it, 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 png files and the pictures folder."
$ git status

On branch main
nothing to commit, working tree clean

As a bonus, using .gitignore helps us avoid accidentally adding files to the repository that we don’t want to track:

$ git add a.png

The following paths are ignored by one of your .gitignore files:
a.png
Use -f if you really want to add them.

If we really want to override our ignore settings, we can use git add -f to force Git to add something. For example, git add -f a.png. We can also always see the status of ignored files if we want:

$ git status --ignored

On branch main
Ignored files:
 (use "git add -f <file>..." to include in what will be committed)

        a.png
        b.png
        c.png
        pictures/

nothing to commit, working tree clean

Challenge

Ignoring Nested Files

Given a directory structure that looks like:

pictures/cake
pictures/pizza

How would you ignore only pictures/cake and not pictures/pizza?

Solution

If you only want to ignore the contents of pictures/cake, you can change your .gitignore to ignore only the /cake/ subfolder by adding the following line to your .gitignore:

pictures/cake/

This line will ensure only the contents of pictures/cake is ignored, and not the contents of pictures/pizza.

As with most programming issues, there are a few alternative ways that one may ensure this ignore rule is followed. The “Ignoring Nested Files: Variation” exercise has a slightly different directory structure that presents an alternative solution. Further, the discussion page has more detail on ignore rules.

Challenge

Including Specific Files

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

Solution

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

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

The exclamation point operator will include a previously excluded entry.

Note also that, if you’ve previously committed .png files in this lesson, they will not be ignored with this new rule. Only future additions of .png files to the root directory will be ignored.

Challenge

Ignoring Nested Files: Variation

Given a directory structure that looks similar to the earlier Nested Files exercise, but with a slightly different directory structure:

pictures/cake
pictures/pizza
pictures/pie
pictures/brownie

How would you ignore all of the contents in the pictures folder, but not pictures/pie?

Hint: think a bit about how you created an exception with the ! operator before.

Solution

If you want to ignore the contents of pictures/ but not those of pictures/pie/, you can change your .gitignore to ignore the contents of pictures folder, but create an exception for the contents of the pictures/pie subfolder. Your .gitignore would look like this:

pictures/*              # ignore everything in pictures folder
!pictures/pie/          # do not ignore pictures/data/ contents

Challenge

Ignoring all data Files in a Directory

Assuming you have an empty .gitignore file, and given a directory structure that looks like:

pictures/data/location/gps/a.dat
pictures/data/location/gps/b.dat
pictures/data/location/gps/c.dat
pictures/data/location/gps/info.txt
pictures/plots

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

Solution

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

Challenge

Ignoring all data Files in the repository

Let us assume you have many .csv files in different subdirectories of your repository. For example, you might have:

results/a.csv
data/experiment_1/b.csv
data/experiment_2/c.csv
data/experiment_2/variation_1/d.csv

How do you ignore all the .csv files, without explicitly listing the names of the corresponding folders?

Solution

In the .gitignore file, write:

**/*.csv

This will ignore all the .csv files, regardless of their position in the directory tree. You can still include some specific exception with the exclamation point operator.

Challenge

The Order of Rules

Given a .gitignore file with the following contents:

*.csv
!*.csv

What will be the result?

Solution

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

Challenge

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.

Write one .gitignore entry that excludes files of the form log_01, log_02, etc.
Test your “ignore pattern” by creating some dummy files of the form log_01, etc.
You find that the file log_01 is very important after all, add it to the tracked files without changing the .gitignore again.
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

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

Key Points

The .gitignore file is a text file that tells Git which files to track and which to ignore in the repository.
You can list specific files or folders to be ignored by Git, or you can include files that would normally be ignored.