stub out hook manager when hooks are disabled in tests

Gitaly has a `GITALY_TESTING_NO_GIT_HOOKS` environment variable
to disable git hooks during tests. Currently, it only skips configuring
the interal API client but leaves the hook manager in place. This causes
nil pointer dereferencing panics when executing code that would invoke
hooks when the environment variable is set.

This commit fixes the problem by stubbing out the whole hook manager
when the environment variable is set.

2 files changed, 37 insertions, 3 deletions

diff --git a/cmd/gitaly/main.go b/cmd/gitaly/main.go
index 73f1a38fa..eb4316575 100644
--- a/cmd/gitaly/main.go
+++ b/cmd/gitaly/main.go
@@ -127,6 +127,7 @@ func run(b *bootstrap.Bootstrap) error {
 	var gitlabAPI hook.GitlabAPI
 	var err error
 
+	hookManager := hook.Manager(hook.DisabledManager{})
 	if config.SkipHooks() {
 		log.Warn("skipping GitLab API client creation since hooks are bypassed via GITALY_TESTING_NO_GIT_HOOKS")
 	} else {
@@ -134,10 +135,12 @@ func run(b *bootstrap.Bootstrap) error {
 		if err != nil {
 			log.Fatalf("could not create GitLab API client: %v", err)
 		}
-	}
 
-	hookManager := hook.NewManager(config.NewLocator(config.Config), gitlabAPI, config.Config)
-	prometheus.MustRegister(hookManager)
+		hm := hook.NewManager(config.NewLocator(config.Config), gitlabAPI, config.Config)
+		prometheus.MustRegister(hm)
+
+		hookManager = hm
+	}
 
 	conns := client.NewPoolWithOptions(
 		client.WithDialer(client.HealthCheckDialer(client.DialContext)),
diff --git a/internal/gitaly/hook/disabled_manager.go b/internal/gitaly/hook/disabled_manager.go
new file mode 100644
index 000000000..192739aef
--- /dev/null
+++ b/internal/gitaly/hook/disabled_manager.go
@@ -0,0 +1,31 @@
+package hook
+
+import (
+	"context"
+	"io"
+
+	"gitlab.com/gitlab-org/gitaly/proto/go/gitalypb"
+)
+
+// DisabledManager never executes hooks and simply returns a nil error.
+type DisabledManager struct{}
+
+// PreReceiveHook ignores its parameters and returns a nil error.
+func (DisabledManager) PreReceiveHook(context.Context, *gitalypb.Repository, []string, io.Reader, io.Writer, io.Writer) error {
+	return nil
+}
+
+// PostReceiveHook ignores its parameters and returns a nil error.
+func (DisabledManager) PostReceiveHook(context.Context, *gitalypb.Repository, []string, []string, io.Reader, io.Writer, io.Writer) error {
+	return nil
+}
+
+// UpdateHook ignores its parameters and returns a nil error.
+func (DisabledManager) UpdateHook(context.Context, *gitalypb.Repository, string, string, string, []string, io.Writer, io.Writer) error {
+	return nil
+}
+
+// ReferenceTransactionHook ignores its parameters and returns a nil error.
+func (DisabledManager) ReferenceTransactionHook(context.Context, ReferenceTransactionState, []string, io.Reader) error {
+	return nil
+}