Initial feature-flagged go/ruby switch

.gitignore

@@ -12,6 +12,7 @@ tags
 custom_hooks
 hooks/*.d
 /go_build
+/bin/gitlab-shell
 /bin/gitaly-upload-pack
 /bin/gitaly-receive-pack
 /bin/gitaly-upload-archive

config.yml.example

@@ -49,3 +49,6 @@ log_level: INFO
 # Set to true to see real usernames in the logs instead of key ids, which is easier to follow, but
 # incurs an extra API call on every gitlab-shell command.
 audit_usernames: false
+
+# Feature flag: go or ruby
+experimental: false

go/cmd/gitlab-shell/main.go

+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"syscall"
+
+	"gitlab.com/gitlab-org/gitlab-shell/go/internal/config"
+)
+
+func experiment() {
+	fmt.Println("Experiment! nothing works!")
+	os.Exit(1)
+}
+
+func main() {
+	root := filepath.Dir(os.Args[0])
+	ruby := filepath.Join(root, "gitlab-shell-ruby")
+
+	config, err := config.New()
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	if config.Experimental {
+		experiment()
+	} else {
+		execErr := syscall.Exec(ruby, os.Args, os.Environ())
+		if execErr != nil {
+			fmt.Fprintf(os.Stderr, "Failed to exec(%q): %v\n", ruby, execErr)
+			os.Exit(1)
+		}
+	}
+}

go/internal/config/config.go

@@ -14,9 +14,10 @@ const (
 )
 
 type Config struct {
-	RootDir   string
-	LogFile   string `yaml:"log_file"`
-	LogFormat string `yaml:"log_format"`
+	RootDir      string
+	LogFile      string `yaml:"log_file"`
+	LogFormat    string `yaml:"log_format"`
+	Experimental bool   `yaml:"experimental"`
 }
 
 func New() (*Config, error) {

go/internal/config/config_test.go

@@ -8,14 +8,16 @@ import (
 func TestConfigLogFile(t *testing.T) {
 	testRoot := "/foo/bar"
 	testCases := []struct {
-		yaml   string
-		path   string
-		format string
+		yaml         string
+		path         string
+		format       string
+		experimental bool
 	}{
 		{path: "/foo/bar/gitlab-shell.log", format: "text"},
 		{yaml: "log_file: my-log.log", path: "/foo/bar/my-log.log", format: "text"},
 		{yaml: "log_file: /qux/my-log.log", path: "/qux/my-log.log", format: "text"},
 		{yaml: "log_format: json", path: "/foo/bar/gitlab-shell.log", format: "json"},
+		{yaml: "experimental: true", path: "/foo/bar/gitlab-shell.log", format: "text", experimental: true},
 	}
 
 	for _, tc := range testCases {
@@ -25,6 +27,10 @@ func TestConfigLogFile(t *testing.T) {
 				t.Fatal(err)
 			}
 
+			if cfg.Experimental != tc.experimental {
+				t.Fatalf("expected %v, got %v", tc.experimental, cfg.Experimental)
+			}
+
 			if cfg.LogFile != tc.path {
 				t.Fatalf("expected %q, got %q", tc.path, cfg.LogFile)
 			}