Should not look for `.git` or `.git/info/exclude` if `git-ignore = false`

I have set `git-ignore = false` in my config. Yet `strace` shows tons of the following commands when running a backup:

```
[pid 2301286] stat("/1/5/e/e/0/.git", 0x7f49ced334a0) = -1 ENOENT (No such file or directory)
[pid 2301286] stat("/1/5/e/e/0/.git/info/exclude", 0x7f49ced331c0) = -1 ENOENT (No such file or directory)
```
