nix/coordinator: support specific private SSH keys

Signed-off-by: Raito Bezarius <raito@lix.systems>

buildbot_nix/__init__.py

@@ -310,6 +310,7 @@ class GitWithRetry(steps.Git):
 
 def nix_eval_config(
     project: GerritProject,
+    gerrit_private_key: str,
     worker_names: list[str],
     supported_systems: list[str],
     eval_lock: util.MasterLock,
@@ -326,7 +327,8 @@ def nix_eval_config(
             repourl="git://git@git.lix.systems/lix-project/lix",
             mode="full",
             retry=[60, 60],
-            timeout=3600
+            timeout=3600,
+            sshPrivateKey=gerrit_private_key
         ),
     )
     drv_gcroots_dir = util.Interpolate(
@@ -570,12 +572,20 @@ def config_for_project(
             ),
         ],
     )
+    gerrit_private_key = None
+    with open('/var/lib/buildbot/master/id_gerrit', 'r') as f:
+        gerrit_private_key = f.read()
+
+    if gerrit_private_key is None:
+        raise RuntimeError('No gerrit private key to fetch the repositories')
+
     config["builders"].extend(
         [
             # Since all workers run on the same machine, we only assign one of them to do the evaluation.
             # This should prevent exessive memory usage.
             nix_eval_config(
                 project,
+                gerrit_private_key,
                 worker_names,
                 supported_systems=nix_supported_systems,
                 worker_count=nix_eval_worker_count,
@@ -670,6 +680,7 @@ class GerritNixConfigurator(ConfiguratorBase):
         gerrit_server: str,
         gerrit_user: str,
         gerrit_port: int,
+        gerrit_sshkey_path: str,
         url: str,
         nix_supported_systems: list[str],
         nix_eval_worker_count: int | None,
@@ -686,7 +697,7 @@ class GerritNixConfigurator(ConfiguratorBase):
         self.nix_eval_max_memory_size = nix_eval_max_memory_size
         self.nix_eval_worker_count = nix_eval_worker_count
         self.nix_supported_systems = nix_supported_systems
-        self.gerrit_change_source = GerritChangeSource(gerrit_server, gerrit_user, gerritport=gerrit_port)
+        self.gerrit_change_source = GerritChangeSource(gerrit_server, gerrit_user, gerritport=gerrit_port, identity_file=gerrit_sshkey_path)
         self.url = url
         self.cachix = cachix
         if outputs_path is None: