move plumbing from top level package to plumbing (#183)

* plumbing: rename Object -> EncodedObject.

* plumbing/storer: rename ObjectStorer -> EncodedObjectStorer.

* move difftree to plumbing/difftree.

* move diff -> utils/diff

* make Object/Tag/Blob/Tree/Commit/File depend on storer.

* Object and its implementations now depend only on
  storer.EncodedObjectStorer, not git.Repository.
* Tests are decoupled accordingly.

* move Object/Commit/File/Tag/Tree to plumbing/object.

* move Object/Commit/File/Tag/Tree to plumbing/object.
* move checkClose to utils/ioutil.

* move RevListObjects to plumbing/revlist.Objects.

* move DiffTree to plumbing/difftree package.

* rename files with plural nouns to singular

* plumbing/object: add GetBlob/GetCommit/GetTag/GetTree.

1 files changed, 34 insertions, 0 deletions

diff --git a/plumbing/object/commit_walker_test.go b/plumbing/object/commit_walker_test.go
new file mode 100644
index 0000000..67d6695
--- /dev/null
+++ b/plumbing/object/commit_walker_test.go
@@ -0,0 +1,34 @@
+package object
+
+import . "gopkg.in/check.v1"
+
+type CommitWalkerSuite struct {
+	BaseObjectsSuite
+}
+
+var _ = Suite(&CommitWalkerSuite{})
+
+func (s *CommitWalkerSuite) TestWalkerNext(c *C) {
+	commit := s.commit(c, s.Fixture.Head)
+
+	var commits []*Commit
+
+	WalkCommitHistory(commit, func(c *Commit) error {
+		commits = append(commits, c)
+		return nil
+	})
+
+	SortCommits(commits)
+	c.Assert(commits, HasLen, 8)
+
+	expected := []string{
+		"b029517f6300c2da0f4b651b8642506cd6aaf45d", "b8e471f58bcbca63b07bda20e428190409c2db47",
+		"35e85108805c84807bc66a02d91535e1e24b38b9", "a5b8b09e2f8fcb0bb99d3ccb0958157b40890d69",
+		"1669dce138d9b841a518c64b10914d88f5e488ea", "af2d6a6954d532f8ffb47615169c8fdf9d383a1a",
+		"918c48b83bd081e863dbe1b80f8998f058cd8294", "6ecf0ef2c2dffb796033e5a02219af86ec6584e5",
+	}
+
+	for i, commit := range commits {
+		c.Assert(commit.Hash.String(), Equals, expected[i])
+	}
+}