`convert` errors if tempdir is on different filesystem

[lordkekz]

Your project looks really exciting!

I was just trying it out, but there are some issues on my system. Here's one, which I may be able to send a PR for, but I want to report it first to get feedback on how you want to solve it.

My environment

I have my /tmp on a tmpfs and I use impermanence with btrfs to mount persistent directories (like git repos).

What happened

When I tried to run git prole convert (after #95), it failed with the following error:

$ git prole convert
• Converting ~/git to a worktree repository at ~/git/nixos-riscv.
  I'll move the following worktrees to new locations:
  • ~/git/nixos-riscv -> ~/git/nixos-riscv/master
  Additionally, I'll convert the repository to a bare repository.

Error:   × failed to rename file from /home/username/git/nixos-riscv/.git to /tmp/.tmp7ju3mQ/.git
  ╰─▶ Cross-device link (os error 18)

How to solve it

I haven't looked into the codebase enough, but I think that git-prole is trying to move the .git to a tempdir before it rearranges the current directory.

[lordkekz]

The error happens because std::fs::rename errors when source and destination are on different filesystems. For example, in convert.rs#L477.

[9999years]

Huh, that's frustrating. I'm a little surprised that didn't get caught in the tests -- I guess none of the test environments run with the tempdir on a different filesystem, or maybe the whole test suite runs in the tempdir...

I think that we can create a tempdir in the parent of the outer-most worktree and use that to fix this.