refactor(web/cgit-tvl): Move cgit config back out of module

It occured to me yesterday that with the config inside of the module
it is kind of difficult to test cgit locally.

This moves it back to a separate location (//web/cgit-tvl) and makes
the most important things configurable via overrides.

Change-Id: I9b0f4c60b75c31441e1718e63b5b55aba3100aae
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5893
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

ops/modules/cgit/default.nix

@@ -1,92 +0,0 @@
-# Configuration for running the TVL cgit instance using thttpd.
-{ config, depot, lib, pkgs, ... }:
-
-let
-  inherit (pkgs) writeText;
-
-  cfg = config.services.depot.cgit;
-
-  cgitConfig = writeText "cgitrc" ''
-    # Global configuration
-    virtual-root=/
-    enable-http-clone=0
-    readme=:README.md
-    about-filter=${depot.tools.cheddar.about-filter}/bin/cheddar-about
-    source-filter=${depot.tools.cheddar}/bin/cheddar
-    enable-log-filecount=1
-    enable-log-linecount=1
-    enable-follow-links=1
-    enable-blame=1
-    mimetype-file=${pkgs.mime-types}/etc/mime.types
-    logo=https://static.tvl.fyi/${depot.web.static.drvHash}/logo-animated.svg
-
-    # Repository configuration
-    repo.url=depot
-    repo.path=/var/lib/gerrit/git/depot.git/
-    repo.desc=monorepo for the virus lounge
-    repo.owner=The Virus Lounge
-    repo.clone-url=https://code.tvl.fyi/depot.git
-  '';
-
-  thttpdConfig = writeText "thttpd.conf" ''
-    port=${toString cfg.port}
-    dir=${depot.third_party.cgit}/cgit
-    nochroot
-    novhost
-    cgipat=**.cgi
-  '';
-
-  # Patched version of thttpd that serves cgit.cgi as the index and
-  # sets the environment variable for pointing cgit at the correct
-  # configuration.
-  #
-  # Things are done this way because recompilation of thttpd is much
-  # faster than cgit.
-  thttpdConfigPatch = writeText "thttpd_cgit_conf.patch" ''
-    diff --git a/libhttpd.c b/libhttpd.c
-    index c6b1622..eef4b73 100644
-    --- a/libhttpd.c
-    +++ b/libhttpd.c
-    @@ -3055,4 +3055,6 @@ make_envp( httpd_conn* hc )
-
-         envn = 0;
-    +    // force cgit to load the correct configuration
-    +    envp[envn++] = "CGIT_CONFIG=${cgitConfig}";
-         envp[envn++] = build_env( "PATH=%s", CGI_PATH );
-     #ifdef CGI_LD_LIBRARY_PATH
-  '';
-
-  thttpdCgit = pkgs.thttpd.overrideAttrs (old: {
-    patches = [
-      ./thttpd_cgi_idx.patch
-      thttpdConfigPatch
-    ];
-  });
-in
-{
-  options.services.depot.cgit = with lib; {
-    enable = mkEnableOption "Run cgit web interface for depot";
-
-    port = mkOption {
-      description = "Port on which cgit should listen";
-      type = types.int;
-      default = 2448;
-    };
-  };
-
-  config = lib.mkIf cfg.enable {
-    systemd.services.cgit = {
-      wantedBy = [ "multi-user.target" ];
-
-      serviceConfig = {
-        Restart = "on-failure";
-        User = "git";
-        Group = "git";
-
-        ExecStart = pkgs.writeShellScript "cgit-launch" ''
-          exec ${thttpdCgit}/bin/thttpd -D -C ${thttpdConfig}
-        '';
-      };
-    };
-  };
-}