Chapter 6 Ignoring Things

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 results
> touch a.dat b.dat c.dat results/a.out results/b.out

and see what Git says:

> git status

# On branch master
# 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 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:

> atom .gitignore

Then add the text in the file:

*.dat
results/

Such that we can look at the text:

> cat .gitignore

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.

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

> 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)

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 "Add the ignore file"
> git status

# On branch master
# 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.dat

# 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:

> git status --ignored

# On branch master
# 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 directory clean