Merge master into staging-next

# Fetchers {#chap-pkgs-fetchers}

Building software with Nix often requires downloading source code and other files from the internet.

`nixpkgs` provides *fetchers* for different protocols and services. Fetchers are functions that simplify downloading files.

To this end, Nixpkgs provides *fetchers*: functions to obtain remote sources via various protocols and services.

## Caveats {#chap-pkgs-fetchers-caveats}

Nixpkgs fetchers differ from built-in fetchers such as [`builtins.fetchTarball`](https://nixos.org/manual/nix/stable/language/builtins.html#builtins-fetchTarball):

- A built-in fetcher will download and cache files at evaluation time and produce a [store path](https://nixos.org/manual/nix/stable/glossary#gloss-store-path).

  A Nixpkgs fetcher will create a ([fixed-output](https://nixos.org/manual/nix/stable/glossary#gloss-fixed-output-derivation)) [derivation](https://nixos.org/manual/nix/stable/language/derivations), and files are downloaded at build time.

- Built-in fetchers will invalidate their cache after [`tarball-ttl`](https://nixos.org/manual/nix/stable/command-ref/conf-file#conf-tarball-ttl) expires, and will require network activity to check if the cache entry is up to date.

  Nixpkgs fetchers only re-download if the specified hash changes or the store object is not otherwise available.

- Built-in fetchers do not use [substituters](https://nixos.org/manual/nix/stable/command-ref/conf-file#conf-substituters).

  Derivations produced by Nixpkgs fetchers will use any configured binary cache transparently.

This significantly reduces the time needed to evaluate the entirety of Nixpkgs, and allows [Hydra](https://nixos.org/hydra) to retain and re-distribute sources used by Nixpkgs in the [public binary cache](https://cache.nixos.org).

For these reasons, built-in fetchers are not allowed in Nixpkgs source code.

The following table shows an overview of the differences:

Fetchers create [fixed output derivations](https://nixos.org/manual/nix/stable/#fixed-output-drvs) from downloaded files.

Nix can reuse the downloaded files via the hash of the resulting derivation.

| Fetchers | Download | Output | Cache | Re-download when |

|-|-|-|-|-|

| `builtins.fetch*` | evaluation time | store path | `/nix/store`, `~/.cache/nix` | `tarball-ttl` expires, cache miss in `~/.cache/nix`, output store object not in local store |

| `pkgs.fetch*` | build time | derivation | `/nix/store`, substituters | output store object not available |

## Caveats {#chap-pkgs-fetchers-caveats}

The fact that the hash belongs to the Nix derivation output and not the file itself can lead to confusion.

For example, consider the following fetcher:

  This use case makes little sense for files that are already in the store.

  This should be a separate abstraction as e.g. `pkgs.drvLayout` instead, which could have a similar interface but be specific to derivations.

  Additional capabilities could be supported that can't be done at evaluation time, such as renaming files, creating new directories, setting executable bits, etc.

- (+) An API for filtering/transforming Nix store paths could be much more powerful,

  because it's not limited to just what is possible at evaluation time with `builtins.path`.

  Operations such as moving and adding files would be supported.

### Single files

- `services.hedgedoc` has been heavily refactored, reducing the amount of declared options in the module. Most of the options should still work without any changes. Some options have been deprecated, as they no longer have any effect. See [#244941](https://github.com/NixOS/nixpkgs/pull/244941) for more details.

- The [services.woodpecker-server](#opt-services.woodpecker-server.environmentFile) type was changed to list of paths to be more consistent to the woodpecker-agent module

- The module [services.ankisyncd](#opt-services.ankisyncd.package) has been switched to [anki-sync-server-rs](https://github.com/ankicommunity/anki-sync-server-rs) from the old python version, which was difficult to update, had not been updated in a while, and did not support recent versions of anki.

Unfortunately all servers supporting new clients (newer version of anki-sync-server, anki's built in sync server and this new rust package) do not support the older sync protocol that was used in the old server, so such old clients will also need updating and in particular the anki package in nixpkgs is also being updated in this release.

The module update takes care of the new config syntax and the data itself (user login and cards) are compatible, so users of the module will be able to just log in again after updating both client and server without any extra action.

        description = lib.mdDoc "woodpecker-server config environment variables, for other options read the [documentation](https://woodpecker-ci.org/docs/administration/server-config)";

      };

      environmentFile = lib.mkOption {

        type = lib.types.nullOr lib.types.path;

        default = null;

        type = with lib.types; coercedTo path (f: [ f ]) (listOf path);

        default = [ ];

        example = "/root/woodpecker-server.env";

        description = lib.mdDoc ''

          File to load environment variables

          StateDirectoryMode = "0700";

          UMask = "0007";

          ConfigurationDirectory = "woodpecker-server";

          EnvironmentFile = lib.optional (cfg.environmentFile != null) cfg.environmentFile;

          EnvironmentFile = cfg.environmentFile;

          ExecStart = "${cfg.package}/bin/woodpecker-server";

          Restart = "on-failure";

          RestartSec = 15;

    services.grafana.settings.rendering = mkIf cfg.provisionGrafana {

      server_url = "http://localhost:${toString cfg.settings.service.port}/render";

      callback_url = "http://localhost:${toString config.services.grafana.settings.server.http_port}";

      callback_url = "http://${config.services.grafana.settings.server.http_addr}:${toString config.services.grafana.settings.server.http_port}";

    };

    services.grafana-image-renderer.chromium = mkDefault pkgs.chromium;