.gitignore exclude folder but include specific subfolder

Commit 59856de from Karsten Blees (kblees) for Git 1.9/2.0 (Q1 2014) clarifies that case:

gitignore.txt: clarify recursive nature of excluded directories

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. (*)
(*: unless certain conditions are met in git 2.8+, see below)
Git doesn't list excluded directories for performance reasons, so any patterns on contained files have no effect, no matter where they are defined.

Put a backslash ("\") in front of the first "!" for patterns that begin with a literal "!", for example, "\!important!.txt".

Example to exclude everything except a specific directory foo/bar (note the /* - without the slash, the wildcard would also exclude everything within foo/bar):

 --------------------------------------------------------------
     $ cat .gitignore
     # exclude everything except directory foo/bar
     /*
     !/foo
     /foo/*
     !/foo/bar
 --------------------------------------------------------------

In your case:

application/*
!application/**/
application/language/*
!application/language/**/
!application/language/gr/**

You must white-list folders first, before being able to white-list files within a given folder.

---

Update Feb/March 2016:

Note that with git 2.9.x/2.10 (mid 2016?), it might be possible to re-include a file if a parent directory of that file is excluded if there is no wildcard in the path re-included.

Nguyễn Thái Ngọc Duy (pclouds) is trying to add this feature:

• commit 506d8f1 for git v2.7.0, reverted in commit 76b620d git v2.8.0-rc0
• commit 5e57f9c git v2.8.0-rc0,... reverted(!) in commit 5cee3493 git 2.8.0.

So with git 2.9+, this could have actually worked, but was ultimately reverted:

application/
!application/language/gr/

@Chris Johnsen's answer is great, but with a newer versions of Git (1.8.2 or later), there is a double asterisk pattern you can leverage for a bit more shorthand solution:

# assuming the root folder you want to ignore is 'application'
application/**/*

# the subfolder(s) you want to track:
!application/language/gr/

This way you don't have to "unignore" parent directory of the subfolder you want to track.

---

With Git 2.17.0 (Not sure how early before this version. Possibly back to 1.8.2), using the ** pattern combined with excludes for each subdirectory leading up to your file(s) works. For example:

# assuming the root folder you want to ignore is 'application'
application/**

# Explicitly track certain content nested in the 'application' folder:
!application/language/
!application/language/gr/
!application/language/gr/** # Example adding all files & folder in the 'gr' folder
!application/language/gr/SomeFile.txt # Example adding specific file in the 'gr' folder

I've found only this actually works.

**/node_modules/*
!**/node_modules/keep-dir

If you exclude application/, then everything under it will always be excluded (even if some later negative exclusion pattern (“unignore”) might match something under application/).

To do what you want, you have to “unignore” every parent directory of anything that you want to “unignore”. Usually you end up writing rules for this situation in pairs: ignore everything in a directory, but not some certain subdirectory.

# you can skip this first one if it is not already excluded by prior patterns
!application/

application/*
!application/language/

application/language/*
!application/language/gr/

Note
The trailing /* is significant:

• The pattern dir/ excludes a directory named dir and (implicitly) everything under it.
  With dir/, Git will never look at anything under dir, and thus will never apply any of the “un-exclude” patterns to anything under dir.
• The pattern dir/* says nothing about dir itself; it just excludes everything under dir. With dir/*, Git will process the direct contents of dir, giving other patterns a chance to “un-exclude” some bit of the content (!dir/sub/).