fix(git): add support for credential.useHttpPath

In some scenarios the host machines git config sets
`credential.useHttpPath=true` but the git config in either the agent or
actual workspace doesn't.
Until now this would break git credential forwarding because we
wouldn't provide the `path` component to the machines git credential
helper.

pkg/agent/tunnelserver/tunnelserver.go

@@ -214,6 +214,21 @@ func (t *tunnelServer) GitCredentials(ctx context.Context, message *tunnel.Messa
 		credentials.Username = t.gitCredentialsOverride.username
 		credentials.Password = t.gitCredentialsOverride.token
 	} else {
+		if t.workspace.Source.GitRepository != "" {
+			path, err := gitcredentials.GetHTTPPath(ctx, gitcredentials.GetHttpPathParameters{
+				Host:        credentials.Host,
+				Protocol:    credentials.Protocol,
+				CurrentPath: credentials.Path,
+				Repository:  t.workspace.Source.GitRepository,
+			})
+			if err != nil {
+				return nil, fmt.Errorf("get http path: %w", err)
+			}
+			// Set the credentials `path` field to the path component of the git repository URL.
+			// This allows downstream credential helpers to figure out which passwords needs to be fetched
+			credentials.Path = path
+		}
+
 		response, err := gitcredentials.GetCredentials(credentials)
 		if err != nil {
 			return nil, perrors.Wrap(err, "get git response")

pkg/gitcredentials/gitcredentials.go

@@ -3,6 +3,7 @@ package gitcredentials
 import (
 	"context"
 	"fmt"
+	netUrl "net/url"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -224,6 +225,41 @@ func GetCredentials(requestObj *GitCredentials) (*GitCredentials, error) {
 	return Parse(string(stdout))
 }
 
+type GetHttpPathParameters struct {
+	Host        string
+	Protocol    string
+	CurrentPath string
+	Repository  string
+}
+
+// GetHTTPPath checks for gits `credential.useHttpPath` setting for a given host+protocol and returns the path component
+// of `GitCredential` if the setting is true
+func GetHTTPPath(ctx context.Context, params GetHttpPathParameters) (string, error) {
+	// No need to look up the HTTP Path if we already have one
+	if params.CurrentPath != "" {
+		return params.CurrentPath, nil
+	}
+
+	// Check if we need to respect gits `credential.useHttpPath`
+	// The actual format for the key is `credential.$PROTOCOL://$HOST.useHttpPath`, i.e. `credential.https://github.com.useHttpPath`
+	configKey := fmt.Sprintf("credential.%s://%s.useHttpPath", params.Protocol, params.Host)
+	out, err := git.CommandContext(ctx, "config", "--get", configKey).Output()
+	if err != nil {
+		return "", fmt.Errorf("inspect useHttpPath for host %s: %w", params.Host, err)
+	}
+	if strings.TrimSpace(string(out)) != "true" {
+		return "", nil
+	}
+	// We can assume the GitRepository is always HTTP(S) based as otherwise we wouldn't
+	// request credentials for it
+	url, err := netUrl.Parse(params.Repository)
+	if err != nil {
+		return "", fmt.Errorf("parse workspace repository: %w", err)
+	}
+
+	return url.Path, nil
+}
+
 func SetupGpgGitKey(gitSignKey string) error {
 	gitConfigCmd := exec.Command("git", []string{"config", "--global", "user.signingKey", gitSignKey}...)