Fall back to full Git clone if shallow clone is not supported (#775)

## Changes
Git repos hosted over HTTP do not support shallow cloning. This PR adds
retry logic if we detect shallow cloning is not supported.

Note I saw the match string `dumb http transport does not support
shallow capabilities` being reported in for different hosts on the
internet, so this should work accross a large class of git servers.
Howerver, it's not strictly necessary to have the `--depth` flag so we
can remove it if this issue is reported again.

## Tests
Tested manually. `bundle init` successfully downloads the private HTTP
repo reported during by internal user.

libs/git/clone.go

@@ -25,31 +25,23 @@ type cloneOptions struct {
 
 	// Local path to clone repository at
 	TargetPath string
+
+	// If true, the repository is shallow cloned
+	Shallow bool
 }
 
 func (opts cloneOptions) args() []string {
-	args := []string{"clone", opts.RepositoryUrl, opts.TargetPath, "--depth=1", "--no-tags"}
+	args := []string{"clone", opts.RepositoryUrl, opts.TargetPath, "--no-tags"}
 	if opts.Reference != "" {
 		args = append(args, "--branch", opts.Reference)
 	}
+	if opts.Shallow {
+		args = append(args, "--depth=1")
+	}
 	return args
 }
 
-func Clone(ctx context.Context, url, reference, targetPath string) error {
+func (opts cloneOptions) clone(ctx context.Context) error {
-	// We assume only the repository name has been if input does not contain any
-	// `/` characters and the url is only made up of alphanumeric characters and
-	// ".", "_" and "-". This repository is resolved again databricks github account.
-	fullUrl := url
-	if githubRepoRegex.MatchString(url) {
-		fullUrl = strings.Join([]string{githubUrl, databricksOrg, url}, "/")
-	}
-
-	opts := cloneOptions{
-		Reference:     reference,
-		RepositoryUrl: fullUrl,
-		TargetPath:    targetPath,
-	}
-
 	cmd := exec.CommandContext(ctx, "git", opts.args()...)
 	var cmdErr bytes.Buffer
 	cmd.Stderr = &cmdErr
@@ -70,3 +62,29 @@ func Clone(ctx context.Context, url, reference, targetPath string) error {
 	}
 	return nil
 }
+
+func Clone(ctx context.Context, url, reference, targetPath string) error {
+	// We assume only the repository name has been if input does not contain any
+	// `/` characters and the url is only made up of alphanumeric characters and
+	// ".", "_" and "-". This repository is resolved again databricks github account.
+	fullUrl := url
+	if githubRepoRegex.MatchString(url) {
+		fullUrl = strings.Join([]string{githubUrl, databricksOrg, url}, "/")
+	}
+
+	opts := cloneOptions{
+		Reference:     reference,
+		RepositoryUrl: fullUrl,
+		TargetPath:    targetPath,
+		Shallow:       true,
+	}
+
+	err := opts.clone(ctx)
+	// Git repos hosted via HTTP do not support shallow cloning. We try with
+	// a deep clone this time
+	if err != nil && strings.Contains(err.Error(), "dumb http transport does not support shallow capabilities") {
+		opts.Shallow = false
+		return opts.clone(ctx)
+	}
+	return err
+}

libs/git/clone_test.go

@@ -10,17 +10,27 @@ import (
 
 func TestGitCloneArgs(t *testing.T) {
 	// case: No branch / tag specified. In this case git clones the default branch
-	assert.Equal(t, []string{"clone", "abc", "/def", "--depth=1", "--no-tags"}, cloneOptions{
+	assert.Equal(t, []string{"clone", "abc", "/def", "--no-tags", "--depth=1"}, cloneOptions{
 		Reference:     "",
 		RepositoryUrl: "abc",
 		TargetPath:    "/def",
+		Shallow:       true,
 	}.args())
 
 	// case: A branch is specified.
-	assert.Equal(t, []string{"clone", "abc", "/def", "--depth=1", "--no-tags", "--branch", "my-branch"}, cloneOptions{
+	assert.Equal(t, []string{"clone", "abc", "/def", "--no-tags", "--branch", "my-branch", "--depth=1"}, cloneOptions{
 		Reference:     "my-branch",
 		RepositoryUrl: "abc",
 		TargetPath:    "/def",
+		Shallow:       true,
+	}.args())
+
+	// case: deep cloning
+	assert.Equal(t, []string{"clone", "abc", "/def", "--no-tags"}, cloneOptions{
+		Reference:     "",
+		RepositoryUrl: "abc",
+		TargetPath:    "/def",
+		Shallow:       false,
 	}.args())
 }