blame: fix edge case with missing \n in content length causing mismatched length error

blame.go

@@ -123,14 +123,25 @@ func newLine(author, text string, date time.Time, hash plumbing.Hash) *Line {
 }
 
 func newLines(contents []string, commits []*object.Commit) ([]*Line, error) {
-	if len(contents) != len(commits) {
-		return nil, errors.New("contents and commits have different length")
+	lcontents := len(contents)
+	lcommits := len(commits)
+
+	if lcontents != lcommits {
+		if lcontents == lcommits-1 && contents[lcontents-1] != "\n" {
+			contents = append(contents, "\n")
+		} else {
+			return nil, errors.New("contents and commits have different length")
+		}
 	}
-	result := make([]*Line, 0, len(contents))
+
+	result := make([]*Line, 0, lcontents)
 	for i := range contents {
-		l := newLine(commits[i].Author.Email, contents[i], commits[i].Author.When, commits[i].Hash)
-		result = append(result, l)
+		result = append(result, newLine(
+			commits[i].Author.Email, contents[i],
+			commits[i].Author.When, commits[i].Hash,
+		))
 	}
+
 	return result, nil
 }
 

blame_test.go

@@ -2,6 +2,7 @@ package git
 
 import (
 	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/object"
 
 	. "gopkg.in/check.v1"
 	"gopkg.in/src-d/go-git-fixtures.v3"
@@ -13,6 +14,31 @@ type BlameSuite struct {
 
 var _ = Suite(&BlameSuite{})
 
+func (s *BlameSuite) TestNewLines(c *C) {
+	h := plumbing.NewHash("ce9f123d790717599aaeb76bc62510de437761be")
+	lines, err := newLines([]string{"foo"}, []*object.Commit{{
+		Hash:    h,
+		Message: "foo",
+	}})
+
+	c.Assert(err, IsNil)
+	c.Assert(lines, HasLen, 1)
+	c.Assert(lines[0].Text, Equals, "foo")
+	c.Assert(lines[0].Hash, Equals, h)
+}
+
+func (s *BlameSuite) TestNewLinesWithNewLine(c *C) {
+	lines, err := newLines([]string{"foo"}, []*object.Commit{
+		{Message: "foo"},
+		{Message: "bar"},
+	})
+
+	c.Assert(err, IsNil)
+	c.Assert(lines, HasLen, 2)
+	c.Assert(lines[0].Text, Equals, "foo")
+	c.Assert(lines[1].Text, Equals, "\n")
+}
+
 type blameTest struct {
 	repo   string
 	rev    string