Blame support for files

This also includes a diff package and revlist package (needed by
blame)

Some extra packfiles (<1MB) are also included, to be used as fixtures in
the tests.

2 files changed, 95 insertions, 0 deletions

diff --git a/diff/diff.go b/diff/diff.go
new file mode 100644
index 0000000..b840ad6
--- /dev/null
+++ b/diff/diff.go
@@ -0,0 +1,45 @@
+// Package diff implements line oriented diffs, similar to the ancient
+// Unix diff command.
+//
+// The current implementation is just a wrapper around Sergi's
+// go-diff/diffmatchpatch library, which is a go port of Neil
+// Fraser's google-diff-match-patch code
+package diff
+
+import (
+	"bytes"
+
+	"github.com/sergi/go-diff/diffmatchpatch"
+)
+
+// Do computes the (line oriented) modifications needed to turn the src
+// string into the dst string.
+func Do(src, dst string) (diffs []diffmatchpatch.Diff) {
+	dmp := diffmatchpatch.New()
+	wSrc, wDst, warray := dmp.DiffLinesToChars(src, dst)
+	diffs = dmp.DiffMain(wSrc, wDst, false)
+	diffs = dmp.DiffCharsToLines(diffs, warray)
+	return diffs
+}
+
+// Dst computes and returns the destination text.
+func Dst(diffs []diffmatchpatch.Diff) string {
+	var text bytes.Buffer
+	for _, d := range diffs {
+		if d.Type != diffmatchpatch.DiffDelete {
+			text.WriteString(d.Text)
+		}
+	}
+	return text.String()
+}
+
+// Src computes and returns the source text
+func Src(diffs []diffmatchpatch.Diff) string {
+	var text bytes.Buffer
+	for _, d := range diffs {
+		if d.Type != diffmatchpatch.DiffInsert {
+			text.WriteString(d.Text)
+		}
+	}
+	return text.String()
+}
diff --git a/diff/diff_ext_test.go b/diff/diff_ext_test.go
new file mode 100644
index 0000000..5ab8c7d
--- /dev/null
+++ b/diff/diff_ext_test.go
@@ -0,0 +1,50 @@
+package diff_test
+
+import (
+	"testing"
+
+	. "gopkg.in/check.v1"
+
+	"gopkg.in/src-d/go-git.v2/diff"
+)
+
+func Test(t *testing.T) { TestingT(t) }
+
+type suiteCommon struct{}
+
+var _ = Suite(&suiteCommon{})
+
+var diffTests = [...]struct {
+	src string // the src string to diff
+	dst string // the dst string to diff
+}{
+	// equal inputs
+	{"", ""},
+	{"a", "a"},
+	{"a\n", "a\n"},
+	{"a\nb", "a\nb"},
+	{"a\nb\n", "a\nb\n"},
+	{"a\nb\nc", "a\nb\nc"},
+	{"a\nb\nc\n", "a\nb\nc\n"},
+	// missing '\n'
+	{"", "\n"},
+	{"\n", ""},
+	{"a", "a\n"},
+	{"a\n", "a"},
+	{"a\nb", "a\nb"},
+	{"a\nb\n", "a\nb\n"},
+	{"a\nb\nc", "a\nb\nc"},
+	{"a\nb\nc\n", "a\nb\nc\n"},
+	// generic
+	{"a\nbbbbb\n\tccc\ndd\n\tfffffffff\n", "bbbbb\n\tccc\n\tDD\n\tffff\n"},
+}
+
+func (s *suiteCommon) TestCountLines(c *C) {
+	for i, t := range diffTests {
+		diffs := diff.Do(t.src, t.dst)
+		src := diff.Src(diffs)
+		dst := diff.Dst(diffs)
+		c.Assert(src, Equals, t.src, Commentf("subtest %d, src=%q, dst=%q, bad calculated src", i, t.src, t.dst))
+		c.Assert(dst, Equals, t.dst, Commentf("subtest %d, src=%q, dst=%q, bad calculated dst", i, t.src, t.dst))
+	}
+}