Re: [PATCH] gc: notice gc processes run by other users

> Since 64a99eb4 git gc refuses to run without the --force option if
> another gc process on the same repository is already running.
>
> However, if the repository is shared and user A runs git gc on the
> repository and while that gc is still running user B runs git gc on
> the same repository the gc process run by user A will not be noticed
> and the gc run by user B will go ahead and run.
>
> The problem is that the kill(pid, 0) test fails with an EPERM error
> since user B is not allowed to signal processes owned by user A
> (unless user B is root).
>
> Update the test to recognize an EPERM error as meaning the process
> exists and another gc should not be run (unless --force is given).