If You Get IOException: Unknown repository format "null"; expected "0" In NetBeans + Git
If NetBeans (7+) is not able to find the following entry in .git/config:
[core]
repositoryformatversion = 0
it throws an IOException with the message: "Unknown repository format "null"; expected "0".
To solve the problem open .git/config and add the entry above or execute: git config --add core.repositoryformatversion 0 from command line.
