3 files changed, 167 insertions, 0 deletions
diff --git a/plumbing/object/commit.go b/plumbing/object/commit.go
index b70128c..fad3dac 100644
--- a/plumbing/object/commit.go
+++ b/plumbing/object/commit.go
@@ -265,6 +265,32 @@ func (b *Commit) Encode(o plumbing.EncodedObject) error {
 	return err
 }
 
+// Stats shows the status of commit.
+func (c *Commit) Stats() (FileStats, error) {
+	// Get the previous commit.
+	ci := c.Parents()
+	parentCommit, err := ci.Next()
+	if err != nil {
+		if err == io.EOF {
+			emptyNoder := treeNoder{}
+			parentCommit = &Commit{
+				Hash: emptyNoder.hash,
+				// TreeHash: emptyNoder.parent.Hash,
+				s: c.s,
+			}
+		} else {
+			return nil, err
+		}
+	}
+
+	patch, err := parentCommit.Patch(c)
+	if err != nil {
+		return nil, err
+	}
+
+	return getFileStatsFromFilePatches(patch.FilePatches()), nil
+}
+
 func (c *Commit) String() string {
 	return fmt.Sprintf(
 		"%s %s\nAuthor: %s\nDate:   %s\n\n%s\n",
diff --git a/plumbing/object/commit_test.go b/plumbing/object/commit_test.go
index 2d04e77..e84160b 100644
--- a/plumbing/object/commit_test.go
+++ b/plumbing/object/commit_test.go
@@ -258,3 +258,29 @@ RUysgqjcpT8+iQM1PblGfHR4XAhuOqN5Fx06PSaFZhqvWFezJ28/CLyX5q+oIVk=
 	c.Assert(err, IsNil)
 	c.Assert(decoded.PGPSignature, Equals, pgpsignature)
 }
+
+func (s *SuiteCommit) TestStat(c *C) {
+	aCommit := s.commit(c, plumbing.NewHash("6ecf0ef2c2dffb796033e5a02219af86ec6584e5"))
+	fileStats, err := aCommit.Stats()
+	c.Assert(err, IsNil)
+
+	c.Assert(fileStats[0].Name, Equals, "vendor/foo.go")
+	c.Assert(fileStats[0].Addition, Equals, 7)
+	c.Assert(fileStats[0].Deletion, Equals, 0)
+	c.Assert(fileStats[0].String(), Equals, " vendor/foo.go | 7 +++++++\n")
+
+	// Stats for another commit.
+	aCommit = s.commit(c, plumbing.NewHash("918c48b83bd081e863dbe1b80f8998f058cd8294"))
+	fileStats, err = aCommit.Stats()
+	c.Assert(err, IsNil)
+
+	c.Assert(fileStats[0].Name, Equals, "go/example.go")
+	c.Assert(fileStats[0].Addition, Equals, 142)
+	c.Assert(fileStats[0].Deletion, Equals, 0)
+	c.Assert(fileStats[0].String(), Equals, " go/example.go | 142 +++++++++++++++++++++++++++++++++++++++++++++++++++++\n")
+
+	c.Assert(fileStats[1].Name, Equals, "php/crappy.php")
+	c.Assert(fileStats[1].Addition, Equals, 259)
+	c.Assert(fileStats[1].Deletion, Equals, 0)
+	c.Assert(fileStats[1].String(), Equals, " php/crappy.php | 259 ++++++++++++++++++++++++++++++++++++++++++++++++++++\n")
+}
diff --git a/plumbing/object/patch.go b/plumbing/object/patch.go
index d413114..a920631 100644
--- a/plumbing/object/patch.go
+++ b/plumbing/object/patch.go
@@ -4,6 +4,8 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"math"
+	"strings"
 
 	"gopkg.in/src-d/go-git.v4/plumbing"
 	"gopkg.in/src-d/go-git.v4/plumbing/filemode"
@@ -105,6 +107,10 @@ func (p *Patch) Encode(w io.Writer) error {
 	return ue.Encode(p)
 }
 
+func (p *Patch) Stats() FileStats {
+	return getFileStatsFromFilePatches(p.FilePatches())
+}
+
 func (p *Patch) String() string {
 	buf := bytes.NewBuffer(nil)
 	err := p.Encode(buf)
@@ -185,3 +191,112 @@ func (t *textChunk) Content() string {
 func (t *textChunk) Type() fdiff.Operation {
 	return t.op
 }
+
+// FileStat stores the status of changes in content of a file.
+type FileStat struct {
+	Name     string
+	Addition int
+	Deletion int
+}
+
+func (fs FileStat) String() string {
+	return printStat([]FileStat{fs})
+}
+
+// FileStats is a collection of FileStat.
+type FileStats []FileStat
+
+func (fileStats FileStats) String() string {
+	return printStat(fileStats)
+}
+
+func printStat(fileStats []FileStat) string {
+	padLength := float64(len(" "))
+	newlineLength := float64(len("\n"))
+	separatorLength := float64(len("|"))
+	// Soft line length limit. The text length calculation below excludes
+	// length of the change number. Adding that would take it closer to 80,
+	// but probably not more than 80, until it's a huge number.
+	lineLength := 72.0
+
+	// Get the longest filename and longest total change.
+	var longestLength float64
+	var longestTotalChange float64
+	for _, fs := range fileStats {
+		if int(longestLength) < len(fs.Name) {
+			longestLength = float64(len(fs.Name))
+		}
+		totalChange := fs.Addition + fs.Deletion
+		if int(longestTotalChange) < totalChange {
+			longestTotalChange = float64(totalChange)
+		}
+	}
+
+	// Parts of the output:
+	// <pad><filename><pad>|<pad><changeNumber><pad><+++/---><newline>
+	// example: " main.go | 10 +++++++--- "
+
+	// <pad><filename><pad>
+	leftTextLength := padLength + longestLength + padLength
+
+	// <pad><number><pad><+++++/-----><newline>
+	// Excluding number length here.
+	rightTextLength := padLength + padLength + newlineLength
+
+	totalTextArea := leftTextLength + separatorLength + rightTextLength
+	heightOfHistogram := lineLength - totalTextArea
+
+	// Scale the histogram.
+	var scaleFactor float64
+	if longestTotalChange > heightOfHistogram {
+		// Scale down to heightOfHistogram.
+		scaleFactor = float64(longestTotalChange / heightOfHistogram)
+	} else {
+		scaleFactor = 1.0
+	}
+
+	finalOutput := ""
+	for _, fs := range fileStats {
+		addn := float64(fs.Addition)
+		deln := float64(fs.Deletion)
+		adds := strings.Repeat("+", int(math.Floor(addn/scaleFactor)))
+		dels := strings.Repeat("-", int(math.Floor(deln/scaleFactor)))
+		finalOutput += fmt.Sprintf(" %s | %d %s%s\n", fs.Name, (fs.Addition + fs.Deletion), adds, dels)
+	}
+
+	return finalOutput
+}
+
+func getFileStatsFromFilePatches(filePatches []fdiff.FilePatch) FileStats {
+	var fileStats FileStats
+
+	for _, fp := range filePatches {
+		cs := FileStat{}
+		from, to := fp.Files()
+		if from == nil {
+			// New File is created.
+			cs.Name = to.Path()
+		} else if to == nil {
+			// File is deleted.
+			cs.Name = from.Path()
+		} else if from.Path() != to.Path() {
+			// File is renamed. Not supported.
+			// cs.Name = fmt.Sprintf("%s => %s", from.Path(), to.Path())
+		} else {
+			cs.Name = from.Path()
+		}
+
+		for _, chunk := range fp.Chunks() {
+			switch chunk.Type() {
+			case fdiff.Add:
+				cs.Addition += strings.Count(chunk.Content(), "\n")
+			case fdiff.Delete:
+				cs.Deletion += strings.Count(chunk.Content(), "\n")
+			}
+		}
+
+		fileStats = append(fileStats, cs)
+	}
+
+	return fileStats
+}