escape forward slashes in gitlab branch name

scm/driver/gitlab/git.go

@@ -7,6 +7,8 @@ package gitlab
 import (
 	"context"
 	"fmt"
+	"net/url"
+	"strings"
 	"time"
 
 	"github.com/drone/go-scm/scm"
@@ -33,6 +35,11 @@ func (s *gitService) FindBranch(ctx context.Context, repo, name string) (*scm.Re
 }
 
 func (s *gitService) FindCommit(ctx context.Context, repo, ref string) (*scm.Commit, *scm.Response, error) {
+	// if the reference is a branch, ensure forward slashes
+	// in the branch name are escaped.
+	if strings.Contains("ref", "/") {
+		ref = url.PathEscape(ref)
+	}
 	path := fmt.Sprintf("api/v4/projects/%s/repository/commits/%s", encode(repo), scm.TrimRef(ref))
 	out := new(commit)
 	res, err := s.client.do(ctx, "GET", path, nil, out)