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.

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 receipts
$ touch a.png b.png c.png receipts/a.jpg receipts/b.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
	receipts/

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
$ cat .gitignore

*.png
receipts/

These patterns tell Git to ignore any file whose name ends in .png and everything in the receipts 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 receipts folder."
$ git status

On branch main
nothing to commit, working directory clean

As a bonus, using .gitignore helps us avoid accidentally adding to the repository files 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.dat. 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
        receipts/

nothing to commit, working directory clean

Ignoring Nested Files

Given a directory structure that looks like:

receipts/data
receipts/plots

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

Solution

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

receipts/plots/

This line will ensure only the contents of receipts/plots is ignored, and not the contents of receipts/data.

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.

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 because you’ve previously committed .png files in this lesson they will not be ignored with this new rule. Only future additions of .png files added to the root directory will be ignored.

Ignoring Nested Files: Variation

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

receipts/data
receipts/images
receipts/plots
receipts/analysis

How would you ignore all of the contents in the receipts folder, but not receipts/data?

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

Solution

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

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

Ignoring all data Files in a Directory

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

receipts/data/market_position/gps/a.dat
receipts/data/market_position/gps/b.dat
receipts/data/market_position/gps/c.dat
receipts/data/market_position/gps/info.txt
receipts/plots

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

Solution

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

Ignoring all data Files in the repository

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

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

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

Solution

In the .gitignore file, write:

**/*.dat               

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

The Order of Rules

Given a .gitignore file with the following contents:

*.dat
!*.dat

What will be the result?

Solution

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