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gitutils.go
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gitutils.go
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package git // import "github.com/docker/docker/builder/remotecontext/git"
import (
"net/http"
"net/url"
"os"
"path/filepath"
"strings"
"github.com/moby/sys/symlink"
"github.com/pkg/errors"
exec "golang.org/x/sys/execabs"
)
type gitRepo struct {
remote string
ref string
subdir string
}
// Clone clones a repository into a newly created directory which
// will be under "docker-build-git"
func Clone(remoteURL string) (string, error) {
repo, err := parseRemoteURL(remoteURL)
if err != nil {
return "", err
}
return cloneGitRepo(repo)
}
func cloneGitRepo(repo gitRepo) (checkoutDir string, err error) {
fetch := fetchArgs(repo.remote, repo.ref)
root, err := os.MkdirTemp("", "docker-build-git")
if err != nil {
return "", err
}
defer func() {
if err != nil {
os.RemoveAll(root)
}
}()
if out, err := gitWithinDir(root, "init"); err != nil {
return "", errors.Wrapf(err, "failed to init repo at %s: %s", root, out)
}
// Add origin remote for compatibility with previous implementation that
// used "git clone" and also to make sure local refs are created for branches
if out, err := gitWithinDir(root, "remote", "add", "origin", repo.remote); err != nil {
return "", errors.Wrapf(err, "failed add origin repo at %s: %s", repo.remote, out)
}
if output, err := gitWithinDir(root, fetch...); err != nil {
return "", errors.Wrapf(err, "error fetching: %s", output)
}
checkoutDir, err = checkoutGit(root, repo.ref, repo.subdir)
if err != nil {
return "", err
}
cmd := exec.Command("git", "submodule", "update", "--init", "--recursive", "--depth=1")
cmd.Dir = root
output, err := cmd.CombinedOutput()
if err != nil {
return "", errors.Wrapf(err, "error initializing submodules: %s", output)
}
return checkoutDir, nil
}
func parseRemoteURL(remoteURL string) (gitRepo, error) {
repo := gitRepo{}
if !isGitTransport(remoteURL) {
remoteURL = "https://" + remoteURL
}
var fragment string
if strings.HasPrefix(remoteURL, "git@") {
// git@.. is not an URL, so cannot be parsed as URL
parts := strings.SplitN(remoteURL, "#", 2)
repo.remote = parts[0]
if len(parts) == 2 {
fragment = parts[1]
}
repo.ref, repo.subdir = getRefAndSubdir(fragment)
} else {
u, err := url.Parse(remoteURL)
if err != nil {
return repo, err
}
repo.ref, repo.subdir = getRefAndSubdir(u.Fragment)
u.Fragment = ""
repo.remote = u.String()
}
if strings.HasPrefix(repo.ref, "-") {
return gitRepo{}, errors.Errorf("invalid refspec: %s", repo.ref)
}
return repo, nil
}
func getRefAndSubdir(fragment string) (ref string, subdir string) {
refAndDir := strings.SplitN(fragment, ":", 2)
ref = "master"
if len(refAndDir[0]) != 0 {
ref = refAndDir[0]
}
if len(refAndDir) > 1 && len(refAndDir[1]) != 0 {
subdir = refAndDir[1]
}
return
}
func fetchArgs(remoteURL string, ref string) []string {
args := []string{"fetch"}
if supportsShallowClone(remoteURL) {
args = append(args, "--depth", "1")
}
return append(args, "origin", "--", ref)
}
// Check if a given git URL supports a shallow git clone,
// i.e. it is a non-HTTP server or a smart HTTP server.
func supportsShallowClone(remoteURL string) bool {
if scheme := getScheme(remoteURL); scheme == "http" || scheme == "https" {
// Check if the HTTP server is smart
// Smart servers must correctly respond to a query for the git-upload-pack service
serviceURL := remoteURL + "/info/refs?service=git-upload-pack"
// Try a HEAD request and fallback to a Get request on error
res, err := http.Head(serviceURL) // #nosec G107
if err != nil || res.StatusCode != http.StatusOK {
res, err = http.Get(serviceURL) // #nosec G107
if err == nil {
res.Body.Close()
}
if err != nil || res.StatusCode != http.StatusOK {
// request failed
return false
}
}
if res.Header.Get("Content-Type") != "application/x-git-upload-pack-advertisement" {
// Fallback, not a smart server
return false
}
return true
}
// Non-HTTP protocols always support shallow clones
return true
}
func checkoutGit(root, ref, subdir string) (string, error) {
// Try checking out by ref name first. This will work on branches and sets
// .git/HEAD to the current branch name
if output, err := gitWithinDir(root, "checkout", ref); err != nil {
// If checking out by branch name fails check out the last fetched ref
if _, err2 := gitWithinDir(root, "checkout", "FETCH_HEAD"); err2 != nil {
return "", errors.Wrapf(err, "error checking out %s: %s", ref, output)
}
}
if subdir != "" {
newCtx, err := symlink.FollowSymlinkInScope(filepath.Join(root, subdir), root)
if err != nil {
return "", errors.Wrapf(err, "error setting git context, %q not within git root", subdir)
}
fi, err := os.Stat(newCtx)
if err != nil {
return "", err
}
if !fi.IsDir() {
return "", errors.Errorf("error setting git context, not a directory: %s", newCtx)
}
root = newCtx
}
return root, nil
}
func gitWithinDir(dir string, args ...string) ([]byte, error) {
a := []string{"--work-tree", dir, "--git-dir", filepath.Join(dir, ".git")}
return git(append(a, args...)...)
}
func git(args ...string) ([]byte, error) {
return exec.Command("git", args...).CombinedOutput()
}
// isGitTransport returns true if the provided str is a git transport by inspecting
// the prefix of the string for known protocols used in git.
func isGitTransport(str string) bool {
if strings.HasPrefix(str, "git@") {
return true
}
switch getScheme(str) {
case "git", "http", "https", "ssh":
return true
}
return false
}
// getScheme returns addresses' scheme in lowercase, or an empty
// string in case address is an invalid URL.
func getScheme(address string) string {
u, err := url.Parse(address)
if err != nil {
return ""
}
return u.Scheme
}