Hi,

I recently ran into a race condition when using two different instances of git.Repo objects in two different threads.

Inside repo.index.add(), some functions are decorated with the git_working_dir decorator. This decorator changes the process working directory to the one of repository, performs some system calls, then returns the working dir back to the initial value.

If two threads perform repo.index.add(), even on two independent Repo() objects, the working directory of the entire process could be permanently modified. Moreover, system calls done by index.add() may fail. For example lstat() will be executed with a relative file name assuming a wrong absolute path.

For example:

1. working dir (wd) is /home/user
2. git_working_dir is entered in thread 1. (/home/user is registered, wd changed to /repo1)
3. git_working_dir is entered in thread 2. (/repo1 is registered, wd changed to /repo2)
4. git_working_dir is exited in thread 1. (wd restored to /home/user)
5. git_working_dir is exited in thread 2. (wd restored to /repo1)
   now the process wd is /repo1

I believe I could work around this issue by creating git object directly rather than adding to the index then committing, but I thought you may be interested to know about the issue.

Radu