Git 'fatal: Unable to write new index file'

In my case, the disk ran out of space, so I had to delete files from the hard drive to make space.

I've been having this same problem for the last few days. Basically, without my knowledge the entire repo had been moved to a new filesystem, when I tried to run git status, it was suddenly reporting that every file in the repo had been udpated.

Possible solutions

So, after much google scouring, I tried the following:

• changing .git permssions (same issue)
• changing .git/index permissions (same issue)
• git add-ing all the changes to commit (same issue)
• git rm-ing deleted files, since they were reporting file name too long errors (same issue)
• git reset (soft|Head|Hard) (same issue)
• git clean (same issue)
• turning off windows defender (same issue)
• updating git (same issue)
• different git clients (i use gitbash) (same issue)
• drinking 2 coffees instead of 1 (same issue)

tl:dr - dirty solution

The only thing that managed to solve the issue was to copy the index file, delete the original and rename the copy.

I know its not really a 'solution' but now its magically working ><, with all files / branches intact. If anyone knows why this might have work, do tell.