1 files changed, 111 insertions, 0 deletions
diff --git a/storage/filesystem/dotgit/repository_filesystem.go b/storage/filesystem/dotgit/repository_filesystem.go
new file mode 100644
index 0000000..8d243ef
--- /dev/null
+++ b/storage/filesystem/dotgit/repository_filesystem.go
@@ -0,0 +1,111 @@
+package dotgit
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/go-git/go-billy/v5"
+)
+
+// RepositoryFilesystem is a billy.Filesystem compatible object wrapper
+// which handles dot-git filesystem operations and supports commondir according to git scm layout:
+// https://github.com/git/git/blob/master/Documentation/gitrepository-layout.txt
+type RepositoryFilesystem struct {
+	dotGitFs       billy.Filesystem
+	commonDotGitFs billy.Filesystem
+}
+
+func NewRepositoryFilesystem(dotGitFs, commonDotGitFs billy.Filesystem) *RepositoryFilesystem {
+	return &RepositoryFilesystem{
+		dotGitFs:       dotGitFs,
+		commonDotGitFs: commonDotGitFs,
+	}
+}
+
+func (fs *RepositoryFilesystem) mapToRepositoryFsByPath(path string) billy.Filesystem {
+	// Nothing to decide if commondir not defined
+	if fs.commonDotGitFs == nil {
+		return fs.dotGitFs
+	}
+
+	cleanPath := filepath.Clean(path)
+
+	// Check exceptions for commondir (https://git-scm.com/docs/gitrepository-layout#Documentation/gitrepository-layout.txt)
+	switch cleanPath {
+	case fs.dotGitFs.Join(logsPath, "HEAD"):
+		return fs.dotGitFs
+	case fs.dotGitFs.Join(refsPath, "bisect"), fs.dotGitFs.Join(refsPath, "rewritten"), fs.dotGitFs.Join(refsPath, "worktree"):
+		return fs.dotGitFs
+	}
+
+	// Determine dot-git root by first path element.
+	// There are some elements which should always use commondir when commondir defined.
+	// Usual dot-git root will be used for the rest of files.
+	switch strings.Split(cleanPath, string(filepath.Separator))[0] {
+	case objectsPath, refsPath, packedRefsPath, configPath, branchesPath, hooksPath, infoPath, remotesPath, logsPath, shallowPath, worktreesPath:
+		return fs.commonDotGitFs
+	default:
+		return fs.dotGitFs
+	}
+}
+
+func (fs *RepositoryFilesystem) Create(filename string) (billy.File, error) {
+	return fs.mapToRepositoryFsByPath(filename).Create(filename)
+}
+
+func (fs *RepositoryFilesystem) Open(filename string) (billy.File, error) {
+	return fs.mapToRepositoryFsByPath(filename).Open(filename)
+}
+
+func (fs *RepositoryFilesystem) OpenFile(filename string, flag int, perm os.FileMode) (billy.File, error) {
+	return fs.mapToRepositoryFsByPath(filename).OpenFile(filename, flag, perm)
+}
+
+func (fs *RepositoryFilesystem) Stat(filename string) (os.FileInfo, error) {
+	return fs.mapToRepositoryFsByPath(filename).Stat(filename)
+}
+
+func (fs *RepositoryFilesystem) Rename(oldpath, newpath string) error {
+	return fs.mapToRepositoryFsByPath(oldpath).Rename(oldpath, newpath)
+}
+
+func (fs *RepositoryFilesystem) Remove(filename string) error {
+	return fs.mapToRepositoryFsByPath(filename).Remove(filename)
+}
+
+func (fs *RepositoryFilesystem) Join(elem ...string) string {
+	return fs.dotGitFs.Join(elem...)
+}
+
+func (fs *RepositoryFilesystem) TempFile(dir, prefix string) (billy.File, error) {
+	return fs.mapToRepositoryFsByPath(dir).TempFile(dir, prefix)
+}
+
+func (fs *RepositoryFilesystem) ReadDir(path string) ([]os.FileInfo, error) {
+	return fs.mapToRepositoryFsByPath(path).ReadDir(path)
+}
+
+func (fs *RepositoryFilesystem) MkdirAll(filename string, perm os.FileMode) error {
+	return fs.mapToRepositoryFsByPath(filename).MkdirAll(filename, perm)
+}
+
+func (fs *RepositoryFilesystem) Lstat(filename string) (os.FileInfo, error) {
+	return fs.mapToRepositoryFsByPath(filename).Lstat(filename)
+}
+
+func (fs *RepositoryFilesystem) Symlink(target, link string) error {
+	return fs.mapToRepositoryFsByPath(target).Symlink(target, link)
+}
+
+func (fs *RepositoryFilesystem) Readlink(link string) (string, error) {
+	return fs.mapToRepositoryFsByPath(link).Readlink(link)
+}
+
+func (fs *RepositoryFilesystem) Chroot(path string) (billy.Filesystem, error) {
+	return fs.mapToRepositoryFsByPath(path).Chroot(path)
+}
+
+func (fs *RepositoryFilesystem) Root() string {
+	return fs.dotGitFs.Root()
+}