git - Why should I use .gitignore?

Question

Currently, whenever I create a file that I'd like Git to track I simply add it to the index. If I don't add it to the index Git would not "see it". So why should I use a .gitignore file, as opposed to just not adding it to the index?

Answer 1

You'll generally find that adding each and every file one by one can become tedious when your project becomes bigger.

In Java, you may end up with many .class files that you wouldn't want to add to your repository. Similarly, you may end up with many .o files in C, or .pyc in Python (for example).

Having patterns like *.class, *.o, *.pyc in your .gitignore files allows you to ignore those files once and for all. Subsequent git status runs (or similar if you're using a GUI) will not tell you these are new, untracked files, thereby letting you focus on the files that are really new and noticeably untracked.

This can also be useful if you add an entire directory (e.g. git add myproject): this lets you ignore a category of files altogether.