Prepare simple workbench

After detecting an update of a Git ref craft should create a throw-away
Git clone of the repository with the new Git commit checked out. This is
the starting point for executing build and test steps.

Improving performance by tree-less or shallow clones and updating
submodules is not yet implemented.

1 files changed, 46 insertions, 2 deletions

diff --git a/main.go b/main.go
index 08a97b8..86b689d 100644
--- a/main.go
+++ b/main.go
@@ -8,6 +8,8 @@ import (
 	"io"
 	"log"
 	"os"
+	"os/exec"
+	"path/filepath"
 	"strings"
 )
 
@@ -16,8 +18,12 @@ func main() {
 
 	defer log.Println("Exiting craft")
 	log.Println("Starting craft")
-	log.Printf("Git hook type: %s\n", getHookType())
-	log.Printf("Git repository: %s\n", getRepositoryPath())
+
+	hookType := getHookType()
+	log.Printf("Git hook type: %s\n", hookType)
+
+	repo := getRepositoryPath()
+	log.Printf("Git repository: %s\n", repo)
 
 	for {
 		eof, update := getUpdate()
@@ -25,9 +31,47 @@ func main() {
 			break
 		}
 		log.Printf("Git ref update: %s\n", update)
+		commit := update.updated
+		_ = prepareWorkbench(repo, commit)
+	}
+}
+
+func runCommand(name string, args ...string) {
+	log.Printf("%s %s\n", name, strings.Join(args, " "))
+	command := exec.Command(name, args...)
+	err := command.Run()
+	if err != nil {
+		log.Fatal(err)
 	}
 }
 
+func prepareWorkbench(repo string, commit string) string {
+	workbench, err := os.MkdirTemp("", "*-craft")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer os.RemoveAll(workbench)
+
+	runCommand(
+		"git",
+		"clone",
+		repo,
+		workbench,
+	)
+
+	runCommand(
+		"git",
+		"--git-dir",
+		filepath.Join(workbench, ".git"),
+		"--work-tree",
+		workbench,
+		"checkout",
+		commit,
+	)
+
+	return workbench
+}
+
 func getHookType() string {
 	args := len(os.Args)
 	if args != 1 {