'git status' failed with code 128: index uses sdir extension

[Samuel Freiberg]

Hi all, I've been working in the same git repo for a couple weeks, and randomly one day, SourceTree threw me this error while on the "File Status" tab.

`'git status' failed with code 128: error: index uses sdir extension, which we do not understand. Fatal: index file corrupt.`

I'm not sure why this started happening. I reset the index file, but still seeing this error. Any ideas? I haven't seen this one online.