Introduce RepoSpec.

This PR closes a TODO in the fileLoader type to
replace the string representing a git repo url
with a struct called holding validated fields.

New struct is called RepoSpec.

It holds what we need in coming PRs for remote
repo base containment checks, and will also allow
the overlay cycle prevention code to take into
account different host schemes or branches.

The struct is in a new file called repospec.go.
The new file is mostly just a code move of url
parsing code that was in cloner.go.  Git "blame"
history preserved through the move.

No change in execution (see final commit by itself).

pkg/git/repospec.go

@@ -17,25 +17,49 @@ limitations under the License.
 package git
 
 import (
-	"bytes"
-	"io/ioutil"
-	"os/exec"
 	"path/filepath"
 	"regexp"
 	"strings"
 
 	"github.com/pkg/errors"
+	"sigs.k8s.io/kustomize/pkg/fs"
 )
 
-// Cloner is a function that can clone a git repo.
-type Cloner func(url string) (
-	// Directory where the repo is cloned to.
-	checkoutDir string,
-	// Relative path in the checkoutDir to location
-	// of kustomization file.
-	pathInCoDir string,
-	// Any error encountered when cloning.
-	err error)
+// RepoSpec specifies a git repo and a branch and path therein.
+type RepoSpec struct {
+	// Raw, original spec, used to look for cycles.
+	// TODO(monopole): Drop raw, use processed fields instead.
+	raw string
+
+	// Repo, e.g. github.com/kubernetes-sigs/kustomize
+	repo string
+
+	// ConfirmedDir where the repo is cloned to.
+	cloneDir fs.ConfirmedDir
+
+	// Relative path in the repo, and in the cloneDir,
+	// to a Kustomization.
+	path string
+
+	// Branch or tag reference.
+	ref string
+}
+
+func (x *RepoSpec) CloneDir() fs.ConfirmedDir {
+	return x.cloneDir
+}
+
+func (x *RepoSpec) Raw() string {
+	return x.raw
+}
+
+func (x *RepoSpec) AbsPath() string {
+	return x.cloneDir.Join(x.path)
+}
+
+func (x *RepoSpec) Cleaner(fSys fs.FileSystem) func() error {
+	return func() error { return fSys.RemoveAll(x.cloneDir.String()) }
+}
 
 // IsRepoUrl checks if a string is likely a github repo Url.
 func IsRepoUrl(arg string) bool {
@@ -50,61 +74,22 @@ func IsRepoUrl(arg string) bool {
 			isAzureHost(arg) || isAWSHost(arg))
 }
 
-func makeTmpDir() (string, error) {
-	return ioutil.TempDir("", "kustomize-")
-}
-
-func ClonerUsingGitExec(spec string) (
-	checkoutDir string, pathInCoDir string, err error) {
-	gitProgram, err := exec.LookPath("git")
-	if err != nil {
-		return "", "", errors.Wrap(err, "no 'git' program on path")
-	}
-	checkoutDir, err = makeTmpDir()
-	if err != nil {
-		return
-	}
-	repo, pathInCoDir, gitRef, err := parseUrl(spec)
-	if err != nil {
-		return
-	}
-	cmd := exec.Command(
-		gitProgram,
-		"clone",
-		repo,
-		checkoutDir)
-	var out bytes.Buffer
-	cmd.Stdout = &out
-	err = cmd.Run()
-	if err != nil {
-		return "", "",
-			errors.Wrapf(err, "trouble cloning %s", spec)
-	}
-	if gitRef == "" {
-		return
-	}
-	cmd = exec.Command(gitProgram, "checkout", gitRef)
-	cmd.Dir = checkoutDir
-	err = cmd.Run()
-	if err != nil {
-		return "", "",
-			errors.Wrapf(err, "trouble checking out href %s", gitRef)
-	}
-	return checkoutDir, pathInCoDir, nil
-}
-
-func parseUrl(n string) (
-	repo string, path string, gitRef string, err error) {
+func NewRepoSpecFromUrl(n string) (*RepoSpec, error) {
 	host, repo, path, gitRef, err := parseGithubUrl(n)
 	if err != nil {
-		return
+		return nil, err
 	}
 	if isAzureHost(host) || isAWSHost(host) {
 		repo = host + repo
-		return
+	} else {
+		repo = host + repo + ".git"
 	}
-	repo = host + repo + ".git"
-	return
+	return &RepoSpec{raw: n, repo: repo, path: path, ref: gitRef}, nil
+}
+
+func NewRepoSpec(
+	raw string, cloneDir fs.ConfirmedDir, path string) *RepoSpec {
+	return &RepoSpec{raw: raw, cloneDir: cloneDir, path: path}
 }
 
 const (