How can you limit the output of git diff to only certain file types?

git diff is a powerful command that shows changes between two commits, a commit and the working tree, and more. Sometimes, you may want to limit the output of git diff to only specific types of files. You can achieve this using the -- '*.file_extension' syntax or -- ./*.file_extension.

Let’s say you want to see the difference between two commits but only for .txt files. You can do this using the following command:

git diff -- '*.txt'

The above command will display the differences between the current HEAD and the staging area for all files that end with .txt. This is a glob pattern which is recognized by most Unix-style operating systems. You are telling git to only look for files that end with the .txt extension.

If you want to compare a specific commit with another for a specific type of file, let’s say a .js file, you can use the below command:

git diff <commit1>..<commit2> -- '*.js'

In the above command, replace <commit1> and <commit2> with the hash of the commits that you want to compare. This will only show the differences in .js files between those two commits.

Also, it’s worth noting that you can use multiple file types at once. Let’s say you want to see the difference for both .js and .css files. You can do that using:

git diff -- '*.js' '*.css'

If you want to limit the diff to a specific directory, you can do that as well:

git diff -- 'dir/*.js'

This will show differences in all .js files in the dir directory.

Remember to enclose the file pattern in quotes (' ') because, without them, your shell (bash, zsh, etc.) may try to expand the glob pattern before the git command has a chance to read it, which could lead to incorrect results or errors.

In case you’re on a Windows system and facing any issues, use a forward slash (/) before the file extension:

git diff -- ./*.js

This command tells Git to limit the diff to just .js files in the current directory.