Port to Golang

1 files changed, 134 insertions, 0 deletions

diff --git a/internal/service/git.go b/internal/service/git.go
new file mode 100644
index 0000000..ad3a653
--- /dev/null
+++ b/internal/service/git.go
@@ -0,0 +1,134 @@
+package service
+
+import (
+	"errors"
+	"fmt"
+	"net/url"
+	"os"
+	"os/exec"
+	"path"
+	"strings"
+)
+
+const gitDescriptionFile = "description"
+
+func mapExecError(err error) error {
+	if ee, ok := err.(*exec.ExitError); ok {
+		return errors.New(string(ee.Stderr))
+	}
+	return err
+}
+
+// Set the description  for the projects repository.
+func setDescription(repo string, desc string) error {
+	descPath := path.Join(repo, gitDescriptionFile)
+
+	var curDesc string
+	buf, err := os.ReadFile(descPath)
+	if os.IsNotExist(err) {
+		// empty
+	} else if err != nil {
+		return err
+	} else {
+		curDesc = string(buf)
+	}
+
+	if curDesc != desc {
+		err = os.WriteFile(descPath, []byte(desc), 0750)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// Set the remote origin's URL  for the projects repository.
+func setRemoteOrigin(repo string, origin *url.URL) error {
+	cmd := exec.Command("git", "remote", "get-url", "origin")
+	cmd.Dir = repo
+	buf, err := cmd.Output()
+	if err != nil {
+		return fmt.Errorf("getting current project remote origin: %w", err)
+	}
+	currentOrigin := strings.TrimSpace(string(buf))
+
+	if currentOrigin != origin.String() {
+		cmd = exec.Command("git", "remote", "set-url", "origin", origin.String())
+		cmd.Dir = repo
+		err = cmd.Run()
+		if err != nil {
+			err = mapExecError(err)
+			return fmt.Errorf("setting project remote origin: %w", err)
+		}
+	}
+
+	return nil
+}
+
+func getRemoteHeadReference(repo string) (string, error) {
+	cmd := exec.Command("git", "ls-remote", "--symref", "origin", "HEAD")
+	cmd.Dir = repo
+	buf, err := cmd.Output()
+	if err != nil {
+		return "", mapExecError(err)
+	}
+
+	for _, l := range strings.Split(string(buf), "\n") {
+		fields := strings.Fields(l)
+		if len(fields) != 3 {
+			return "", errors.New("unexpected output from 'git ls-remote'")
+		}
+		if fields[0] == "ref:" {
+			return strings.TrimPrefix(fields[1], "refs/heads/"), nil
+		}
+	}
+
+	return "", errors.New("not found")
+}
+
+func MirrorGit(dst *url.URL, src *url.URL, description string) error {
+	if dst.Scheme != "" && dst.Scheme != "file://" {
+		return fmt.Errorf("'%s' scheme not supported", dst.Scheme)
+	}
+
+	if _, err := os.Stat(dst.Path); os.IsNotExist(err) {
+		err = os.MkdirAll(path.Join(dst.Path, ".."), 0750)
+		if err != nil {
+			return fmt.Errorf("creating new mirror: %w", err)
+		}
+
+		cmd := exec.Command("git", "clone", "--bare", "--single-branch", src.String(), dst.String())
+		cmd.Dir = path.Join(dst.Path, "..")
+		err := cmd.Run()
+		if err != nil {
+			err = mapExecError(err)
+			return fmt.Errorf("cloning: %s", err)
+		}
+	}
+
+	err := setDescription(dst.Path, description)
+	if err != nil {
+		return err
+	}
+
+	err = setRemoteOrigin(dst.Path, src)
+	if err != nil {
+		return err
+	}
+
+	branch, err := getRemoteHeadReference(dst.Path)
+	if err != nil {
+		return fmt.Errorf("guessing remote default branch: %w", err)
+	}
+
+	cmd := exec.Command("git", "fetch", "--tags", "origin", branch+":"+branch)
+	cmd.Dir = dst.Path
+	err = cmd.Run()
+	if err != nil {
+		err = mapExecError(err)
+		return fmt.Errorf("fetching project: %s", err)
+	}
+
+	return nil
+}