We've added the variant to `DerivationOutput` to support them, but made
`DerivationOutput::path` partial to avoid actually implementing them.
With this chage, we can all collaborate on "just" removing
`DerivationOutput::path` calls to implement CA derivations.
The `m` acts as termination-symbol when declaring graphics. Because
of this, the `;1m` doesn't have any effect and is directly printed to
the console:
```
$ nix repl
> builtins.fetchGit { /* ... */ }
{ outPath = "/nix/store/s0f0iz4a41cxx2h055lmh6p2d5k5bc6r-source"; rev = "e73e45b723a9a6eecb98bd5f3df395d9ab3633b6"; revCount = ;1m428; shortRev = "e73e45b"; submodules = ;1mfalse; }
```
Introduced by 6403508f5a.
Starting in Catalina, macOS runs a syspolicyd "assessment" that hits the network for each binary/script executable. It does cache these results, but Nix tends to introduce many "new" executables per build. (You can read more about this at https://github.com/NixOS/nix/issues/3789).
This PR adds a temporary, redundant macOS job with these assessments disabled. I'm hoping you can adopt it for a few weeks to help me collect more data on how this affects real projects.
This reduces memory consumption of
nix-instantiate \
-E 'with import <nixpkgs> {}; runCommand "foo" { src = ./blender; } "echo foo"' \
--option nar-buffer-size 10000
(where ./blender is a 1.1 GiB tree) from 1716 to 36 MiB, while still
ensuring that we don't do any write I/O for small source paths (up to
'nar-buffer-size' bytes). The downside is that large paths are now
always written to a temporary location in the store, even if they
produce an already valid store path. Thus, adding large paths might be
slower and run out of disk space. ¯\_(ツ)_/¯ Of course, you can always
restore the old behaviour by setting 'nar-buffer-size' to a very high
value.
"uid-range" provides 65536 UIDs to a build and runs the build as root
in its user namespace. "systemd-cgroup" allows the build to mount the
systemd cgroup controller (needed for running systemd-nspawn and NixOS
containers).
Also, add a configuration option "auto-allocate-uids" which is needed
to enable these features, and some experimental feature gates.
So to enable support for containers you need the following in
nix.conf:
experimental-features = auto-allocate-uids systemd-cgroup
auto-allocate-uids = true
system-features = uid-range systemd-cgroup
