storage: new storage.ErrReferenceHasChanged error and test for CheckAndSetReference

Signed-off-by: Máximo Cuadros <[email protected]>

Author: mcuadros

storage/filesystem/dotgit/dotgit.go

@@ -14,6 +14,7 @@ import (
 
 	"gopkg.in/src-d/go-billy.v4/osfs"
 	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/storage"
 	"gopkg.in/src-d/go-git.v4/utils/ioutil"
 
 	"gopkg.in/src-d/go-billy.v4"
@@ -596,7 +597,7 @@ func (d *DotGit) checkReferenceAndTruncate(f billy.File, old *plumbing.Reference
 		return err
 	}
 	if ref.Hash() != old.Hash() {
-		return fmt.Errorf("reference has changed concurrently")
+		return storage.ErrReferenceHasChanged
 	}
 	_, err = f.Seek(0, io.SeekStart)
 	if err != nil {

storage/memory/storage.go

@@ -13,7 +13,6 @@ import (
 )
 
 var ErrUnsupportedObjectType = fmt.Errorf("unsupported object type")
-var ErrRefHasChanged = fmt.Errorf("reference has changed concurrently")
 
 // Storage is an implementation of git.Storer that stores data on memory, being
 // ephemeral. The use of this storage should be done in controlled envoriments,
@@ -258,7 +257,7 @@ func (r ReferenceStorage) CheckAndSetReference(ref, old *plumbing.Reference) err
 	if old != nil {
 		tmp := r[ref.Name()]
 		if tmp != nil && tmp.Hash() != old.Hash() {
-			return ErrRefHasChanged
+			return storage.ErrReferenceHasChanged
 		}
 	}
 	r[ref.Name()] = ref

storage/storer.go

@@ -1,10 +1,14 @@
 package storage
 
 import (
+	"errors"
+
 	"gopkg.in/src-d/go-git.v4/config"
 	"gopkg.in/src-d/go-git.v4/plumbing/storer"
 )
 
+var ErrReferenceHasChanged = errors.New("reference has changed concurrently")
+
 // Storer is a generic storage of objects, references and any information
 // related to a particular repository. The package gopkg.in/src-d/go-git.v4/storage
 // contains two implementation a filesystem base implementation (such as `.git`)

storage/test/storage_suite.go

@@ -280,6 +280,57 @@ func (s *BaseStorageSuite) TestSetReferenceAndGetReference(c *C) {
 	c.Assert(e.Hash().String(), Equals, "bc9968d75e48de59f0870ffb71f5e160bbbdcf52")
 }
 
+func (s *BaseStorageSuite) TestCheckAndSetReference(c *C) {
+	err := s.Storer.SetReference(
+		plumbing.NewReferenceFromStrings("foo", "482e0eada5de4039e6f216b45b3c9b683b83bfa"),
+	)
+	c.Assert(err, IsNil)
+
+	err = s.Storer.CheckAndSetReference(
+		plumbing.NewReferenceFromStrings("foo", "bc9968d75e48de59f0870ffb71f5e160bbbdcf52"),
+		plumbing.NewReferenceFromStrings("foo", "482e0eada5de4039e6f216b45b3c9b683b83bfa"),
+	)
+	c.Assert(err, IsNil)
+
+	e, err := s.Storer.Reference(plumbing.ReferenceName("foo"))
+	c.Assert(err, IsNil)
+	c.Assert(e.Hash().String(), Equals, "bc9968d75e48de59f0870ffb71f5e160bbbdcf52")
+}
+
+func (s *BaseStorageSuite) TestCheckAndSetReferenceNil(c *C) {
+	err := s.Storer.SetReference(
+		plumbing.NewReferenceFromStrings("foo", "482e0eada5de4039e6f216b45b3c9b683b83bfa"),
+	)
+	c.Assert(err, IsNil)
+
+	err = s.Storer.CheckAndSetReference(
+		plumbing.NewReferenceFromStrings("foo", "bc9968d75e48de59f0870ffb71f5e160bbbdcf52"),
+		nil,
+	)
+	c.Assert(err, IsNil)
+
+	e, err := s.Storer.Reference(plumbing.ReferenceName("foo"))
+	c.Assert(err, IsNil)
+	c.Assert(e.Hash().String(), Equals, "bc9968d75e48de59f0870ffb71f5e160bbbdcf52")
+}
+
+func (s *BaseStorageSuite) TestCheckAndSetReferenceError(c *C) {
+	err := s.Storer.SetReference(
+		plumbing.NewReferenceFromStrings("foo", "c3f4688a08fd86f1bf8e055724c84b7a40a09733"),
+	)
+	c.Assert(err, IsNil)
+
+	err = s.Storer.CheckAndSetReference(
+		plumbing.NewReferenceFromStrings("foo", "bc9968d75e48de59f0870ffb71f5e160bbbdcf52"),
+		plumbing.NewReferenceFromStrings("foo", "482e0eada5de4039e6f216b45b3c9b683b83bfa"),
+	)
+	c.Assert(err, Equals, storage.ErrReferenceHasChanged)
+
+	e, err := s.Storer.Reference(plumbing.ReferenceName("foo"))
+	c.Assert(err, IsNil)
+	c.Assert(e.Hash().String(), Equals, "c3f4688a08fd86f1bf8e055724c84b7a40a09733")
+}
+
 func (s *BaseStorageSuite) TestRemoveReference(c *C) {
 	err := s.Storer.SetReference(
 		plumbing.NewReferenceFromStrings("foo", "bc9968d75e48de59f0870ffb71f5e160bbbdcf52"),