refactor(ops): Split //ops/nixos into different locations r/2482

Splits //ops/nixos into:

* //ops/nixos.nix - utility functions for building systems
* //ops/machines - shared machine definitions (read by readTree)
* //ops/modules - shared NixOS modules (skipped by readTree)

This simplifies working with the configuration fixpoint in whitby, and
is overall a bit more in line with how NixOS systems in user folders
currently work.

Change-Id: I1322ec5cc76c0207c099c05d44828a3df0b3ffc1
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2931
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
Reviewed-by: glittershark <grfn@gws.fyi>

1 files changed, 128 insertions, 0 deletions

diff --git a/ops/modules/monorepo-gerrit.nix b/ops/modules/monorepo-gerrit.nix
new file mode 100644
index 0000000000..eaea386ecd
--- /dev/null
+++ b/ops/modules/monorepo-gerrit.nix
@@ -0,0 +1,128 @@
+# Gerrit configuration for the TVL monorepo
+{ depot, pkgs, config, lib, ... }:
+
+let
+  cfg = config.services.gerrit;
+  gerritHooks = pkgs.runCommandNoCC "gerrit-hooks" {} ''
+    mkdir -p $out
+    ln -s ${depot.ops.besadii}/bin/besadii $out/ref-updated
+  '';
+in {
+  services.gerrit = {
+    enable = true;
+    listenAddress = "[::]:4778"; # 4778 - grrt
+    serverId = "4fdfa107-4df9-4596-8e0a-1d2bbdd96e36";
+    builtinPlugins = [
+      "download-commands"
+      "hooks"
+    ];
+
+    plugins = with depot.third_party.gerrit_plugins; [
+      owners
+      oauth
+      depot.ops.gerrit-tvl
+    ];
+
+    package = depot.third_party.gerrit;
+
+    jvmHeapLimit = "4g";
+
+    settings = {
+      core.packedGitLimit = "100m";
+      log.jsonLogging = true;
+      log.textLogging = false;
+      sshd.advertisedAddress = "code.tvl.fyi:29418";
+      hooks.path = "${gerritHooks}";
+      cache.web_sessions.maxAge = "3 months";
+      plugins.allowRemoteAdmin = false;
+      change.enableAttentionSet = true;
+      change.enableAssignee = false;
+
+      # Configures gerrit for being reverse-proxied by nginx as per
+      # https://gerrit-review.googlesource.com/Documentation/config-reverseproxy.html
+      gerrit = {
+        canonicalWebUrl = "https://cl.tvl.fyi";
+        docUrl = "/Documentation";
+      };
+
+      httpd.listenUrl = "proxy-https://${cfg.listenAddress}";
+
+      download.command = [
+        "checkout"
+        "cherry_pick"
+        "format_patch"
+        "pull"
+      ];
+
+      # Configure for cgit.
+      gitweb = {
+        type = "custom";
+        url = "https://code.tvl.fyi";
+        project = "/";
+        revision = "/commit/?id=\${commit}";
+        branch = "/log/?h=\${branch}";
+        tag = "/tag/?h=\${tag}";
+        roottree = "/tree/?h=\${commit}";
+        file = "/tree/\${file}?h=\${commit}";
+        filehistory = "/log/\${file}?h=\${branch}";
+        linkname = "cgit";
+      };
+
+      # Auto-link panettone bug links
+      commentlink.panettone = {
+        match = "b/(\\\\d+)";
+        html = "<a href=\"https://b.tvl.fyi/issues/$1\">b/$1</a>";
+      };
+
+      # Auto-link other CLs
+      commentlink.gerrit = {
+        match = "cl/(\\\\d+)";
+        html = "<a href=\"https://cl.tvl.fyi/$1\">cl/$1</a>";
+      };
+
+      # Configures integration with CAS, which then integrates with a variety
+      # of backends.
+      auth.type = "OAUTH";
+      plugin.gerrit-oauth-provider-cas-oauth = {
+        root-url = "https://login.tvl.fyi";
+        client-id = "OAUTH-TVL-gerrit-Fv0d8Aizz5";
+        # client-secret is set in /var/lib/gerrit/etc/secure.config.
+      };
+
+      # Use Gerrit's built-in HTTP passwords, rather than trying to use the
+      # password against the backing OAuth provider.
+      auth.gitBasicAuthPolicy = "HTTP";
+
+      # Email sending (emails are relayed via the tazj.in domain's
+      # GSuite currently).
+      #
+      # Note that sendemail.smtpPass is stored in
+      # $site_path/etc/secure.config and is *not* controlled by Nix.
+      #
+      # Receiving email is not currently supported.
+      sendemail = {
+        enable = true;
+        html = false;
+        connectTimeout = "10sec";
+        from = "TVL Code Review <tvlbot@tazj.in>";
+        includeDiff = true;
+        smtpEncryption = "none";
+        smtpServer = "localhost";
+        smtpServerPort = 2525;
+      };
+    };
+  };
+
+  systemd.services.gerrit = {
+    serviceConfig = {
+      # There seems to be no easy way to get `DynamicUser` to play
+      # well with other services (e.g. by using SupplementaryGroups,
+      # which seem to have no effect) so we force the DynamicUser
+      # setting for the Gerrit service to be disabled and reuse the
+      # existing 'git' user.
+      DynamicUser = lib.mkForce false;
+      User = "git";
+      Group = "git";
+    };
+  };
+}