feat(gonf): implement the gonf build cli command

cmd/gonf/cmd_build.go

@@ -0,0 +1,65 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"log/slog"
+	"os"
+	"os/exec"
+)
+
+var (
+	hostFlag string
+)
+
+func cmdBuild(ctx context.Context,
+	f *flag.FlagSet,
+	args []string,
+	getenv func(string) string,
+	stdout, stderr io.Writer,
+) error {
+	f.Init(`gonf build [-FLAG]
+where FLAG can be one or more of`, flag.ContinueOnError)
+	f.StringVar(&hostFlag, "host", "", "(REQUIRED) a valid $GONF_CONFIG/hosts/ subdirectory inside your gonf configurations repository")
+	f.SetOutput(stderr)
+	f.Parse(args)
+	if helpMode {
+		f.SetOutput(stdout)
+		f.Usage()
+	}
+	if hostFlag == "" {
+		f.Usage()
+		return errors.New("Required -host FLAG is missing")
+	}
+	hostDir := configDir + "/hosts/" + hostFlag
+	if info, err := os.Stat(hostDir); err != nil {
+		f.Usage()
+		return fmt.Errorf("Invalid host name %s, the %s directory returned error %+v", hostFlag, hostDir, err)
+	} else if !info.IsDir() {
+		f.Usage()
+		return fmt.Errorf("Invalid host name %s, %s is not a directory", hostFlag, hostDir)
+	}
+	return runBuild(ctx, hostDir)
+}
+
+func runBuild(ctx context.Context, hostDir string) error {
+	wd, err := os.Getwd()
+	defer os.Chdir(wd)
+	os.Chdir(hostDir)
+	if err != nil {
+		slog.Error("build", "hostDir", hostDir, "error", err)
+		return err
+	}
+	cmd := exec.CommandContext(ctx, "go", "build", "-ldflags", "-s -w -extldflags \"-static\"", hostDir)
+	cmd.Env = append(cmd.Environ(), "CGO_ENABLED=0")
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		slog.Error("build", "hostDir", hostDir, "error", err, "combinedOutput", out)
+		return err
+	}
+	slog.Debug("build", "hostDir", hostDir, "combinedOutput", out)
+	return nil
+}

cmd/gonf/main.go

@@ -56,6 +56,7 @@ where FLAG can be one or more of`, flag.ContinueOnError)
 		return errors.New("No command given")
 	}
 	cmd := f.Arg(0)
+	argsTail := f.Args()[1:]
 	switch cmd {
 	case "help":
 		f.SetOutput(stdout)
@@ -71,6 +72,8 @@ where FLAG can be one or more of`, flag.ContinueOnError)
 			}
 		}
 		switch cmd {
+		case "build":
+			return cmdBuild(ctx, f, argsTail, getenv, stdout, stderr)
 		default:
 			f.Usage()
 			return fmt.Errorf("Invalid command: %s", cmd)