"fatal: Not a git repository (or any of the parent directories)" from git status

In my case, was an environment variable GIT_DIR, which I added to access faster.

This also broke all my local repos in SourceTree :(

I just got this message and there is a very simple answer before trying the others. At the parent directory, type git init

This will initialize the directory for git. Then git add and git commit should work.

You have to actually cd into the directory first:

$ git clone git://cfdem.git.sourceforge.net/gitroot/cfdem/liggghts
Cloning into 'liggghts'...
remote: Counting objects: 3005, done.
remote: Compressing objects: 100% (2141/2141), done.
remote: Total 3005 (delta 1052), reused 2714 (delta 827)
Receiving objects: 100% (3005/3005), 23.80 MiB | 2.22 MiB/s, done.
Resolving deltas: 100% (1052/1052), done.

$ git status
fatal: Not a git repository (or any of the parent directories): .git
$ cd liggghts/
$ git status
# On branch master
nothing to commit (working directory clean)