Ignoring Things

Overview

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:

BASH

$ mkdir results
$ touch a.dat b.dat c.dat results/a.out results/b.out

and see what Git says:

BASH

$ git status

OUTPUT

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

	a.dat
	b.dat
	c.dat
	results/

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:

BASH

$ nano .gitignore
$ cat .gitignore

OUTPUT

*.dat
results/

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

Callout

.gitignore Prevents Accidents

The most important rule: never commit sensitive files like passwords, API keys, or private data. Always create a .gitignore to exclude these files before they accidentally get tracked. Once a file is committed to Git history, it’s very difficult to remove completely. Prevention is much easier than remediation.

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

BASH

$ git status

OUTPUT

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 whole flow: dummy files created, .gitignore written, and git status now showing only the .gitignore itself.

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:

BASH

$ git add .gitignore
$ git commit -m "Ignore data files and the results folder"
$ git status

OUTPUT

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:

BASH

$ git add a.dat

OUTPUT

The following paths are ignored by one of your .gitignore files:
a.dat
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:

BASH

$ git status --ignored

OUTPUT

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

        a.dat
        b.dat
        c.dat
        results/

nothing to commit, working tree clean

Challenge

Ignoring Nested Files

Given a directory structure that looks like:

BASH

results/data
results/plots

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

Show me the solution

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:

OUTPUT

results/plots/

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

Challenge

Including Specific Files

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

Show me the solution

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

OUTPUT

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

The exclamation point operator will include a previously excluded entry.

Note also that because you’ve previously committed .dat files in this lesson they will not be ignored with this new rule. Only future additions of .dat files added 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:

BASH

results/data
results/images
results/plots
results/analysis

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

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

Show me the solution

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

OUTPUT

results/*               # ignore everything in results folder
!results/data/          # do not ignore results/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:

BASH

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

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

Show me the solution

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

Challenge

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:

BASH

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?

Show me the solution

In the .gitignore file, write:

OUTPUT

**/*.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.

Challenge

The Order of Rules

Given a .gitignore file with the following contents:

BASH

*.dat
!*.dat

What will be the result?

Show me the 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.

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.

1. Create a few dummy files to work with: touch log_01 log_02 log_03 etc. How would you write one .gitignore entry that excludes all files of the form log_01 log_02 log_03 ? Check that it worked — git status should not list the log files.

2. You find that the file log_01 is very important after all. How would you add it to the tracked files without editing the .gitignore again?

3. What other types of files could sit in your directory that you do not want to track and thus would exclude via .gitignore?

Show me the solution

1. append either log_* as a new entry in your .gitignore
2. track log_01 using git add -f log_01
3. Passwords, other credentials, API keys, large data files, etc.

Key Points

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