What's the difference between Git ignoring directory and directory/*?

Question

I'm confused about what's the correct way to ignore the contents of a directory in git.

Assume I have the following directory structure:

my_project  
     |--www  
         |--1.txt  
         |--2.txt
     |--.gitignore

What's the difference between putting this:

www

And this?

www/*

The reason I'm asking this question is: In git, if a directory is empty, git won't include such empty directory in repository. So I was trying the solution that is add an extra .gitkeep file under the directory so that it won't be empty. When I was trying that solution, if in the .gitignore file, I write like below:

www
!*.gitkeep

It doesn't work(My intention is to ignore all contents under www but keep the directory). But if I try the following:

www/* 
!*.gitkeep

Then it works! So I think it must has some differences between the two approaches.

Answer 1

There're differences among www, www/ and www/*.

Basically from the documentation and my own tests, www find a match with a file or a directory, www/ only matches a directory, while www/* matches directories and files inside www.

I'll only discuss on the differences between www/ and www/* here, since the differences between www and www/ are obvious.

For www/, git ignores the directory www itself, which means git won't even look inside. But for www/*, git checks all files/folders inside www, and ignores all of them with the pattern *. It seems to lead to the same results since git won't track an empty folder www if all its child files/folders are ignored. And indeed the results will be no difference for OP's case with www/ or www/* standalone. But it does make differences if it's combined with other rules.

For example, what if we want to only include www/1.txt but ignore all others inside www?

The following .gitignore won't work.

www/
!www/1.txt

While the following .gitignore works, why?

www/*
!www/1.txt

For the former, git just ignores the directory www, and won't even look inside to include www/1.txt again. The first rule excludes the parent directory www but not www/1.txt, and as a result www/1.txt cannot be "included again".

But for the latter, git first ignores all files/folers under www, and then includes one of them again which is www/1.txt.

For this example, the follwing lines in the documentation may help:

An optional prefix "!" which negates the pattern; any matching file excluded by a previous pattern will become included again. It is not possible to re-include a file if a parent directory of that file is excluded.