@@ -1,7 +1,6 @@

 package git

 import (

-	"fmt"

 	"io/ioutil"

 	"net/http"

 	"net/url"

@@ -98,22 +97,46 @@ func getRefAndSubdir(fragment string) (ref string, subdir string) {

 func fetchArgs(remoteURL string, ref string) []string {

 	args := []string{"fetch", "--recurse-submodules=yes"}

-	shallow := true

-	if urlutil.IsURL(remoteURL) {

-		res, err := http.Head(fmt.Sprintf("%s/info/refs?service=git-upload-pack", remoteURL))

-		if err != nil || res.Header.Get("Content-Type") != "application/x-git-upload-pack-advertisement" {

-			shallow = false

-		}

-	}

-

-	if shallow {

+	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 urlutil.IsURL(remoteURL) {

+		// 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)

+		if err != nil || res.StatusCode != http.StatusOK {

+			res, err = http.Get(serviceURL)

+			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