Fix rm vscode tmp

[mihem]

@b-rodrigues this fixes a bug i had since the beginning in vscode after running rix and took me some time to figure out.

Warning message:
In file(con, "w") :
  cannot open file '/tmp/RtmpRf8FWl/vscode-R/workspace.json': No such file or directory

So vscode-R saves tmp files in tempdir

print(list.files(tempdir(), recursive = TRUE))
[1] "vscode-R/addins.json"    "vscode-R/response.lock" 
[3] "vscode-R/response.log"   "vscode-R/workspace.json"
[5] "vscode-R/workspace.lock"

rix deletes tmp files that are created (which is good i think) but also deletes all other tmp files, e.g. these vscode-R files, which produce these warning in vscode-R.

I tried to fix this by creating a rix_tmp specific folder.
At least in my case this fixes this issue

[b-rodrigues]

So if I understand correctly, the vscode-r extension also uses the same tempdir as the R session? So when you start a session in VS Code and generate a default.nix expression you get that error message?

[mihem]

Yeah, vscode-R seems to also use tempdir. So I you start a R session in VS Code everything works fine. But after you run rix, those temporary files that vscode-R needs are deleted because of rix. So as long as the session continues, you get this warning message. You can just create a new R session and it's gone. But when I tried to debugging the get_cloest_commit stuf, this got really annoying because it was showing up all the time.
In general I would also think that it's dangerous if rix just deleted all temporary files? So it's safer to create a separate folder and only remove this folder when rix is finished.

[b-rodrigues]

At first we actually had a separate temp folder but had many issues with some unit tests and trying to rebuild vignettes. I think that now it should be fine, though, as the vignettes are static now.

[b-rodrigues]

closing in favour of #403 (comment)