Since nix 2.20, `nix-store --add-fixed` doesn't accept paths where the
parent directory is a symlink. On macOS, /tmp is a symlink to
/private/tmp, which causes a "'/tmp' is a symlink" error:
```
$ nix run github:nixos/nixpkgs/24.11-beta#nix-prefetch-git -- --url https://github.com/IFTTT/polo.git --rev 316aa2ac210a45a7fc400ab921831493d5dd21b8 --hash sha256
Initialized empty Git repository in /private/tmp/git-checkout-tmp-1Bf9bIv7/polo-316aa2a/.git/
remote: Enumerating objects: 51, done.
remote: Counting objects: 100% (51/51), done.
remote: Compressing objects: 100% (42/42), done.
remote: Total 51 (delta 8), reused 19 (delta 5), pack-reused 0 (from 0)
Unpacking objects: 100% (51/51), 19.57 KiB | 541.00 KiB/s, done.
From https://github.com/IFTTT/polo
* branch HEAD -> FETCH_HEAD
Switched to a new branch 'fetchgit'
removing `.git'...
error: path '/tmp' is a symlink
```
Avoid this by resolving /tmp to a real directory in all the prefetch scripts
Transform exit handlers of the form
trap cleanup EXIT [INT] [TERM] [QUIT] [HUP] [ERR]
(where cleanup is idempotent)
to
trap cleanup EXIT
This fixes a common bash antipattern.
Each of the above signals causes the script to exit. For each signal,
bash first handles the signal by running `cleanup` and then runs
`cleanup` again when handling EXIT.
(Exception: `vscode/*` prevents the second run of `cleanup` by removing
the trap in cleanup`).
Simplify the cleanup logic by just trapping exit, which is always run
when the script exits due to any of the above signals.
Note: In case of borgbackup, the exit handler is not idempotent, but just
trapping EXIT guarantees that it's only run once.
Fixes a regression on OS X introduced by f83af95.
Don't use --tmpdir for mktemp, because that flag doesn't exist on OS X.
However, using -t is deprecated in GNU coreutils, so as suggested by
@ip1981 we're now using parameter expansion on ${TMPDIR:-/tmp} to
provide /tmp as a fallback if TMPDIR is not set and use it instead.
Also use this approach for nix-prefetch-cvs now in order to stay
consistent.
Reported-by: Vladimir Kirillov <proger@wilab.org.ua>
Tested-by: Igor Pashev <pashev.igor@gmail.com>
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
