git/odb: make Commit and WriteCommit accessible from ObjectDatabase

git/odb/object_db.go

@@ -42,6 +42,17 @@ func (o *ObjectDatabase) Tree(sha []byte) (*Tree, error) {
 	return &t, nil
 }
 
+// Commit returns a *Commit as identified by the SHA given, or an error if one
+// was encountered.
+func (o *ObjectDatabase) Commit(sha []byte) (*Commit, error) {
+	var c Commit
+
+	if err := o.decode(sha, &c); err != nil {
+		return nil, err
+	}
+	return &c, nil
+}
+
 // WriteBlob stores a *Blob on disk and returns the SHA it is uniquely
 // identified by, or an error if one was encountered.
 func (o *ObjectDatabase) WriteBlob(b *Blob) ([]byte, error) {
@@ -68,6 +79,16 @@ func (o *ObjectDatabase) WriteTree(t *Tree) ([]byte, error) {
 	return sha, nil
 }
 
+// WriteCommit stores a *Commit on disk and returns the SHA it is uniquely
+// identified by, or an error if one was encountered.
+func (o *ObjectDatabase) WriteCommit(c *Commit) ([]byte, error) {
+	sha, _, err := o.encode(c)
+	if err != nil {
+		return nil, err
+	}
+	return sha, nil
+}
+
 // encode encodes and saves an object to the storage backend and uses an
 // in-memory buffer to calculate the object's encoded body.
 func (d *ObjectDatabase) encode(object Object) (sha []byte, n int, err error) {

git/odb/object_db_test.go

@@ -9,6 +9,7 @@ import (
 	"io/ioutil"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -72,6 +73,37 @@ func TestDecodeTree(t *testing.T) {
 	}, tree.Entries[0])
 }
 
+func TestDecodeCommit(t *testing.T) {
+	sha := "d7283480bb6dc90be621252e1001a93871dcf511"
+	commitShaHex, err := hex.DecodeString(sha)
+	assert.Nil(t, err)
+
+	var buf bytes.Buffer
+
+	zw := zlib.NewWriter(&buf)
+	fmt.Fprintf(zw, "commit 173\x00")
+	fmt.Fprintf(zw, "tree fcb545d5746547a597811b7441ed8eba307be1ff\n")
+	fmt.Fprintf(zw, "author Taylor Blau <me@ttaylorr.com> 1494620424 -0600\n")
+	fmt.Fprintf(zw, "committer Taylor Blau <me@ttaylorr.com> 1494620424 -0600\n")
+	fmt.Fprintf(zw, "\ninitial commit\n")
+	zw.Close()
+
+	odb := &ObjectDatabase{s: NewMemoryStorer(map[string]io.ReadWriter{
+		sha: &buf,
+	})}
+
+	commit, err := odb.Commit(commitShaHex)
+
+	assert.Nil(t, err)
+	assert.Equal(t, "Taylor Blau", commit.Author.Name)
+	assert.Equal(t, "me@ttaylorr.com", commit.Author.Email)
+	assert.Equal(t, "Taylor Blau", commit.Committer.Name)
+	assert.Equal(t, "me@ttaylorr.com", commit.Committer.Email)
+	assert.Equal(t, "initial commit", commit.Message)
+	assert.Equal(t, 0, len(commit.ParentIds))
+	assert.Equal(t, "fcb545d5746547a597811b7441ed8eba307be1ff", hex.EncodeToString(commit.TreeId))
+}
+
 func TestWriteBlob(t *testing.T) {
 	fs := NewMemoryStorer(make(map[string]io.ReadWriter))
 	odb := &ObjectDatabase{s: fs}
@@ -111,3 +143,29 @@ func TestWriteTree(t *testing.T) {
 	assert.Equal(t, expected, hex.EncodeToString(sha))
 	assert.NotNil(t, fs.fs[hex.EncodeToString(sha)])
 }
+
+func TestWriteCommit(t *testing.T) {
+	fs := NewMemoryStorer(make(map[string]io.ReadWriter))
+	odb := &ObjectDatabase{s: fs}
+
+	when := time.Unix(1494258422, 0)
+	author := &Signature{Name: "John Doe", Email: "john@example.com", When: when}
+	committer := &Signature{Name: "Jane Doe", Email: "jane@example.com", When: when}
+
+	tree := "fcb545d5746547a597811b7441ed8eba307be1ff"
+	treeHex, err := hex.DecodeString(tree)
+	assert.Nil(t, err)
+
+	sha, err := odb.WriteCommit(&Commit{
+		Author:    author,
+		Committer: committer,
+		TreeId:    treeHex,
+		Message:   "initial commit",
+	})
+
+	expected := "5ba51ea684770de6fef57a94734c4f4a02cb361b"
+
+	assert.Nil(t, err)
+	assert.Equal(t, expected, hex.EncodeToString(sha))
+	assert.NotNil(t, fs.fs[hex.EncodeToString(sha)])
+}