…he compressed hash

This change is to simplify [Trustix](https://github.com/tweag/trustix) indexing and makes it possible to reconstruct this URL regardless of the compression used.

In particular this means that https://github.com/tweag/trustix/blob/7c2e9ca597de233846e0b265fb081626ca6c59d8/contrib/nix/nar/nar.go#L61-L71 can be removed and only the bits that are required to establish trust needs to be published in the Trustix build logs.

Where a `RealisedPath` is a store path with its history, meaning either
an opaque path for stuff that has been directly added to the store, or a
`Realisation` for stuff that has been built by a derivation

This is a low-level refactoring that doesn't bring anything by itself
(except a few dozen extra lines of code :/ ), but raising the
abstraction level a bit is important on a number of levels:

- Commands like `nix build` have to query for the realisations after the
  build is finished which is fragile (see
  27905f1 for example). Having them
  oprate directly at the realisation level would avoid that
- Others like `nix copy` currently operate directly on (built) store
  paths, but need a bit more information as they will need to register
  the realisations on the remote side

This allows patching Nix for Hydra with additional overlays, because
`.overrideAttrs` and co. will persist the passthru's

This fixes an issue where derivations with a primary output that is
not "out" would fail with:

$ nix profile install nixpkgs#sqlite
error: opening directory '/nix/store/2a2ydlgyydly5czcc8lg12n6qqkfz863-sqlite-3.34.1-bin': No such file or directory

This happens because while derivations produce every output when
built, you might not have them if you didn't build the derivation
yourself (for instance, the store path was fetch from a binary cache).
This uses outputName provided from DerivationInfo which appears to
match the first output of the derivation.

This makes nix search always go through the first level of an
attribute set, even if it's not a top level attribute. For instance,
you can now list all GHC compilers with:

$ nix search nixpkgs#haskell.compiler
...

This is similar to how nix-env works when you pass in -A.

Co-authored-by: Eelco Dolstra <edolstra@gmail.com>

Co-authored-by: Eelco Dolstra <edolstra@gmail.com>

…arch

Always enter first level of attrset in nix search

Despite being an ugly hack, it can probably be useful in a couple extra
places

In addition to being some ugly template trickery, it was also totally
useless as it was used in only one place where I could replace it by
just a few extra characters

Hopefully this helps to diagnose 'error: unexpected EOF reading a
line' on macOS.

…rst-output

Use derivation output name from toDerivation

Use passthru for perl-bindings, allows Nix patching for Hydra

Add a new Cmd type working on RealisedPaths

We upgrade to lowdown 0.8.0 [1] which contains a fix/improvement to a
behavior mentioned in this issue thread [2] where a big part of
lowdown's API would just call exit(1) on allocation errors since that
is a satisfying behavior for the lowdown binary.

Now lowdown_term_rndr returns 0 if an allocation error occurred which we
check for in libcmd/markdown.cc.

Also the extern "C" { } wrapper around lowdown.h has been removed as it
is not necessary.

[1]: https://github.com/kristapsdz/lowdown/blob/6ca7c855a063d1c77ae0b89405047cc3913a74d8/versions.xml#L987-L1006
[2]: kristapsdz/lowdown#45 (comment)

The configuration was taken from nixpkgs repository and adjusted to
`NixOS/nix`.

A `stale` label was added to the labels (with gray color).

Issues and PRs with `critical` label are excluded from interacting with the
stale bot.

libcmd/markdown: handle allocation errors in lowdown_term_rndr

narinfo: Change NAR URLs to be addressed on the NAR hash instead of the compressed hash

…ead of the compressed hash"

Add Stale bot

Revert "narinfo: Change NAR URLs to be addressed on the NAR hash instead of the compressed hash"

Hook into the evaluation to cache to cache the evaluation of flake
members (stuff like `(builtins.getCache foo).bar.baz`).
Also replaces the old eval cache that was used at the cli level.