storage/filesystem: call initialization explicitely, fixes #408

filesystem.Storage was initializing the gitdir (creating objects
and refs) on NewStorage. But this should be done only on init and
clone operations, not on open.

Now there is a new interface storer.Initializer that storers can
implement if they need any initialization step before init or clone.
filesystem.Storage is one of such implementations.

git.Init and git.Clone now call to the storer Init() method if it
does implement it. Otherwise, it just ignores initialization.

5 files changed, 37 insertions, 15 deletions

diff --git a/plumbing/storer/storer.go b/plumbing/storer/storer.go
index 0b96c0e..863070d 100644
--- a/plumbing/storer/storer.go
+++ b/plumbing/storer/storer.go
@@ -5,3 +5,11 @@ type Storer interface {
 	EncodedObjectStorer
 	ReferenceStorer
 }
+
+// Initializer should be implemented by storers that require to perform any
+// operation when creating a new repository (i.e. git init).
+type Initializer interface{
+	// Init performs initialization of the storer and returns the error, if
+	// any.
+	Init() error
+}
diff --git a/repository.go b/repository.go
index 76be660..35aae52 100644
--- a/repository.go
+++ b/repository.go
@@ -44,6 +44,10 @@ type Repository struct {
 // The worktree Filesystem is optional, if nil a bare repository is created. If
 // the given storer is not empty ErrRepositoryAlreadyExists is returned
 func Init(s storage.Storer, worktree billy.Filesystem) (*Repository, error) {
+	if err := initStorer(s); err != nil {
+		return nil, err
+	}
+
 	r := newRepository(s, worktree)
 	_, err := r.Reference(plumbing.HEAD, false)
 	switch err {
@@ -67,6 +71,15 @@ func Init(s storage.Storer, worktree billy.Filesystem) (*Repository, error) {
 	return r, setWorktreeAndStoragePaths(r, worktree)
 }
 
+func initStorer(s storer.Storer) error {
+	i, ok := s.(storer.Initializer)
+	if !ok {
+		return nil
+	}
+
+	return i.Init()
+}
+
 func setWorktreeAndStoragePaths(r *Repository, worktree billy.Filesystem) error {
 	type fsBased interface {
 		Filesystem() billy.Filesystem
diff --git a/storage/filesystem/internal/dotgit/dotgit.go b/storage/filesystem/internal/dotgit/dotgit.go
index f9f4d79..1af64ab 100644
--- a/storage/filesystem/internal/dotgit/dotgit.go
+++ b/storage/filesystem/internal/dotgit/dotgit.go
@@ -231,7 +231,7 @@ func (d *DotGit) Objects() ([]plumbing.Hash, error) {
 	return objects, nil
 }
 
-// Object return a fs.File poiting the object file, if exists
+// Object return a fs.File pointing the object file, if exists
 func (d *DotGit) Object(h plumbing.Hash) (billy.File, error) {
 	hash := h.String()
 	file := d.fs.Join(objectsPath, hash[0:2], hash[2:40])
diff --git a/storage/filesystem/storage.go b/storage/filesystem/storage.go
index dcb061d..af340d7 100644
--- a/storage/filesystem/storage.go
+++ b/storage/filesystem/storage.go
@@ -12,6 +12,7 @@ import (
 // are not safe to use, see the NewStorage function below.
 type Storage struct {
 	fs billy.Filesystem
+	dir *dotgit.DotGit
 
 	ObjectStorage
 	ReferenceStorage
@@ -24,10 +25,6 @@ type Storage struct {
 // NewStorage returns a new Storage backed by a given `fs.Filesystem`
 func NewStorage(fs billy.Filesystem) (*Storage, error) {
 	dir := dotgit.New(fs)
-	if err := dir.Initialize(); err != nil {
-		return nil, err
-	}
-
 	o, err := newObjectStorage(dir)
 	if err != nil {
 		return nil, err
@@ -35,6 +32,7 @@ func NewStorage(fs billy.Filesystem) (*Storage, error) {
 
 	return &Storage{
 		fs: fs,
+		dir: dir,
 
 		ObjectStorage:    o,
 		ReferenceStorage: ReferenceStorage{dir: dir},
@@ -49,3 +47,7 @@ func NewStorage(fs billy.Filesystem) (*Storage, error) {
 func (s *Storage) Filesystem() billy.Filesystem {
 	return s.fs
 }
+
+func (s *Storage) Init() error {
+	return s.dir.Initialize()
+}
diff --git a/storage/filesystem/storage_test.go b/storage/filesystem/storage_test.go
index 0127489..03d2e86 100644
--- a/storage/filesystem/storage_test.go
+++ b/storage/filesystem/storage_test.go
@@ -1,6 +1,7 @@
 package filesystem
 
 import (
+	"io/ioutil"
 	"testing"
 
 	"gopkg.in/src-d/go-git.v4/storage/test"
@@ -14,31 +15,29 @@ func Test(t *testing.T) { TestingT(t) }
 
 type StorageSuite struct {
 	test.BaseStorageSuite
+	dir string
 }
 
 var _ = Suite(&StorageSuite{})
 
 func (s *StorageSuite) SetUpTest(c *C) {
-	storage, err := NewStorage(osfs.New(c.MkDir()))
+	s.dir = c.MkDir()
+	storage, err := NewStorage(osfs.New(s.dir))
 	c.Assert(err, IsNil)
 
 	s.BaseStorageSuite = test.NewBaseStorageSuite(storage)
 }
 
-func (s *StorageSuite) TestNewStorage(c *C) {
+func (s *StorageSuite) TestFilesystem(c *C) {
 	fs := memfs.New()
 	storage, err := NewStorage(fs)
 	c.Assert(err, IsNil)
-	c.Assert(storage, NotNil)
 
-	_, err = fs.Stat("refs/tags")
-	c.Assert(err, IsNil)
+	c.Assert(storage.Filesystem(), Equals, fs)
 }
 
-func (s *StorageSuite) TestFilesystem(c *C) {
-	fs := memfs.New()
-	storage, err := NewStorage(fs)
+func (s *StorageSuite) TestNewStorageShouldNotAddAnyContentsToDir(c *C) {
+	fis, err := ioutil.ReadDir(s.dir)
 	c.Assert(err, IsNil)
-
-	c.Assert(storage.Filesystem(), Equals, fs)
+	c.Assert(fis, HasLen, 0)
 }