Add Close() method to gogitRepository (#8901) (#8958)

Backport #8901 - Adjusted slightly for 1.9

In investigating #7947 it has become clear that the storage component of go-git repositories needs closing.

This PR adds this Close function and adds the Close functions as necessary.

In TransferOwnership the ctx.Repo.GitRepo is closed if it is open to help prevent the risk of multiple open files.

Fixes #7947

modules/git/repo.go

@@ -17,6 +17,7 @@ import (
 	"strings"
 	"time"
 
+	gitealog "code.gitea.io/gitea/modules/log"
 	"github.com/Unknwon/com"
 	"gopkg.in/src-d/go-billy.v4/osfs"
 	gogit "gopkg.in/src-d/go-git.v4"
@@ -107,6 +108,21 @@ func OpenRepository(repoPath string) (*Repository, error) {
 	}, nil
 }
 
+// Close this repository, in particular close the underlying gogitStorage if this is not nil
+func (repo *Repository) Close() {
+	if repo == nil || repo.gogitStorage == nil {
+		return
+	}
+	if err := repo.gogitStorage.Close(); err != nil {
+		gitealog.Error("Error closing storage: %v", err)
+	}
+}
+
+// GoGitRepo gets the go-git repo representation
+func (repo *Repository) GoGitRepo() *gogit.Repository {
+	return repo.gogitRepo
+}
+
 // IsEmpty Check if repository is empty.
 func (repo *Repository) IsEmpty() (bool, error) {
 	var errbuf strings.Builder