plumbing: diff, Add initial colored output support. Fixes #33.

3 files changed, 206 insertions, 10 deletions

diff --git a/plumbing/format/diff/colorconfig.go b/plumbing/format/diff/colorconfig.go
new file mode 100644
index 0000000..b7c32e6
--- /dev/null
+++ b/plumbing/format/diff/colorconfig.go
@@ -0,0 +1,96 @@
+package diff
+
+import "github.com/go-git/go-git/v5/internal/color"
+
+// A ColorKey is a key into a ColorConfig map and also equal to the key in the
+// diff.color subsection of the config. See
+// https://github.com/git/git/blob/v2.26.2/diff.c#L83-L106.
+type ColorKey string
+
+// ColorKeys.
+const (
+	Context                   ColorKey = "context"
+	Meta                      ColorKey = "meta"
+	Frag                      ColorKey = "frag"
+	Old                       ColorKey = "old"
+	New                       ColorKey = "new"
+	Commit                    ColorKey = "commit"
+	Whitespace                ColorKey = "whitespace"
+	Func                      ColorKey = "func"
+	OldMoved                  ColorKey = "oldMoved"
+	OldMovedAlternative       ColorKey = "oldMovedAlternative"
+	OldMovedDimmed            ColorKey = "oldMovedDimmed"
+	OldMovedAlternativeDimmed ColorKey = "oldMovedAlternativeDimmed"
+	NewMoved                  ColorKey = "newMoved"
+	NewMovedAlternative       ColorKey = "newMovedAlternative"
+	NewMovedDimmed            ColorKey = "newMovedDimmed"
+	NewMovedAlternativeDimmed ColorKey = "newMovedAlternativeDimmed"
+	ContextDimmed             ColorKey = "contextDimmed"
+	OldDimmed                 ColorKey = "oldDimmed"
+	NewDimmed                 ColorKey = "newDimmed"
+	ContextBold               ColorKey = "contextBold"
+	OldBold                   ColorKey = "oldBold"
+	NewBold                   ColorKey = "newBold"
+)
+
+// A ColorConfig is a color configuration. A nil or empty ColorConfig
+// corresponds to no color.
+type ColorConfig map[ColorKey]string
+
+// A ColorConfigOption sets an option on a ColorConfig.
+type ColorConfigOption func(ColorConfig)
+
+// WithColor sets the color for key.
+func WithColor(key ColorKey, color string) ColorConfigOption {
+	return func(cc ColorConfig) {
+		cc[key] = color
+	}
+}
+
+// defaultColorConfig is the default color configuration. See
+// https://github.com/git/git/blob/v2.26.2/diff.c#L57-L81.
+var defaultColorConfig = ColorConfig{
+	Context:                   color.Normal,
+	Meta:                      color.Bold,
+	Frag:                      color.Cyan,
+	Old:                       color.Red,
+	New:                       color.Green,
+	Commit:                    color.Yellow,
+	Whitespace:                color.BgRed,
+	Func:                      color.Normal,
+	OldMoved:                  color.BoldMagenta,
+	OldMovedAlternative:       color.BoldBlue,
+	OldMovedDimmed:            color.Faint,
+	OldMovedAlternativeDimmed: color.FaintItalic,
+	NewMoved:                  color.BoldCyan,
+	NewMovedAlternative:       color.BoldYellow,
+	NewMovedDimmed:            color.Faint,
+	NewMovedAlternativeDimmed: color.FaintItalic,
+	ContextDimmed:             color.Faint,
+	OldDimmed:                 color.FaintRed,
+	NewDimmed:                 color.FaintGreen,
+	ContextBold:               color.Bold,
+	OldBold:                   color.BoldRed,
+	NewBold:                   color.BoldGreen,
+}
+
+// NewColorConfig returns a new ColorConfig.
+func NewColorConfig(options ...ColorConfigOption) ColorConfig {
+	cc := make(ColorConfig)
+	for key, value := range defaultColorConfig {
+		cc[key] = value
+	}
+	for _, option := range options {
+		option(cc)
+	}
+	return cc
+}
+
+// Reset returns the ANSI escape sequence to reset a color set from cc. If cc is
+// nil or empty then no reset is needed so it returns the empty string.
+func (cc ColorConfig) Reset() string {
+	if len(cc) == 0 {
+		return ""
+	}
+	return color.Reset
+}
diff --git a/plumbing/format/diff/unified_encoder.go b/plumbing/format/diff/unified_encoder.go
index f2bc910..7b0c31e 100644
--- a/plumbing/format/diff/unified_encoder.go
+++ b/plumbing/format/diff/unified_encoder.go
@@ -26,9 +26,9 @@ const (
 	tPath  = "+++ %s\n"
 	binary = "Binary files %s and %s differ\n"
 
-	addLine    = "+%s%s"
-	deleteLine = "-%s%s"
-	equalLine  = " %s%s"
+	addLine    = "%s+%s%s%s"
+	deleteLine = "%s-%s%s%s"
+	equalLine  = "%s %s%s%s"
 	noNewLine  = "\n\\ No newline at end of file\n"
 
 	oldMode         = "old mode %o\n"
@@ -57,6 +57,9 @@ type UnifiedEncoder struct {
 	// surrounding a change.
 	ctxLines int
 
+	// colorConfig is the color configuration. The default is no color.
+	color ColorConfig
+
 	buf bytes.Buffer
 }
 
@@ -64,6 +67,12 @@ func NewUnifiedEncoder(w io.Writer, ctxLines int) *UnifiedEncoder {
 	return &UnifiedEncoder{ctxLines: ctxLines, Writer: w}
 }
 
+// SetColor sets e's color configuration and returns e.
+func (e *UnifiedEncoder) SetColor(colorConfig ColorConfig) *UnifiedEncoder {
+	e.color = colorConfig
+	return e
+}
+
 func (e *UnifiedEncoder) Encode(patch Patch) error {
 	e.printMessage(patch.Message())
 
@@ -85,7 +94,7 @@ func (e *UnifiedEncoder) encodeFilePatch(filePatches []FilePatch) error {
 
 		g := newHunksGenerator(p.Chunks(), e.ctxLines)
 		for _, c := range g.Generate() {
-			c.WriteTo(&e.buf)
+			c.WriteTo(&e.buf, e.color)
 		}
 	}
 
@@ -107,6 +116,8 @@ func (e *UnifiedEncoder) header(from, to File, isBinary bool) error {
 	case from == nil && to == nil:
 		return nil
 	case from != nil && to != nil:
+		e.buf.WriteString(e.color[Meta])
+
 		hashEquals := from.Hash() == to.Hash()
 
 		fmt.Fprintf(&e.buf, diffInit, from.Path(), to.Path())
@@ -130,16 +141,22 @@ func (e *UnifiedEncoder) header(from, to File, isBinary bool) error {
 		if !hashEquals {
 			e.pathLines(isBinary, aDir+from.Path(), bDir+to.Path())
 		}
+
+		e.buf.WriteString(e.color.Reset())
 	case from == nil:
+		e.buf.WriteString(e.color[Meta])
 		fmt.Fprintf(&e.buf, diffInit, to.Path(), to.Path())
 		fmt.Fprintf(&e.buf, newFileMode, to.Mode())
 		fmt.Fprintf(&e.buf, indexNoMode, plumbing.ZeroHash, to.Hash())
 		e.pathLines(isBinary, noFilePath, bDir+to.Path())
+		e.buf.WriteString(e.color.Reset())
 	case to == nil:
+		e.buf.WriteString(e.color[Meta])
 		fmt.Fprintf(&e.buf, diffInit, from.Path(), from.Path())
 		fmt.Fprintf(&e.buf, deletedFileMode, from.Mode())
 		fmt.Fprintf(&e.buf, indexNoMode, from.Hash(), plumbing.ZeroHash)
 		e.pathLines(isBinary, aDir+from.Path(), noFilePath)
+		e.buf.WriteString(e.color.Reset())
 	}
 
 	return nil
@@ -302,7 +319,8 @@ type hunk struct {
 	ops       []*op
 }
 
-func (c *hunk) WriteTo(buf *bytes.Buffer) {
+func (c *hunk) WriteTo(buf *bytes.Buffer, color ColorConfig) {
+	buf.WriteString(color[Frag])
 	buf.WriteString(chunkStart)
 
 	if c.fromCount == 1 {
@@ -320,9 +338,10 @@ func (c *hunk) WriteTo(buf *bytes.Buffer) {
 	}
 
 	fmt.Fprintf(buf, chunkEnd, c.ctxPrefix)
+	buf.WriteString(color.Reset())
 
 	for _, d := range c.ops {
-		buf.WriteString(d.String())
+		buf.WriteString(d.String(color))
 	}
 }
 
@@ -348,20 +367,23 @@ type op struct {
 	t    Operation
 }
 
-func (o *op) String() string {
-	var prefix, suffix string
+func (o *op) String(color ColorConfig) string {
+	var setColor, prefix, suffix string
 	switch o.t {
 	case Add:
 		prefix = addLine
+		setColor = color[New]
 	case Delete:
 		prefix = deleteLine
+		setColor = color[Old]
 	case Equal:
 		prefix = equalLine
+		setColor = color[Context]
 	}
 	n := len(o.text)
 	if n > 0 && o.text[n-1] != '\n' {
 		suffix = noNewLine
 	}
 
-	return fmt.Sprintf(prefix, o.text, suffix)
+	return fmt.Sprintf(prefix, setColor, o.text, color.Reset(), suffix)
 }
diff --git a/plumbing/format/diff/unified_encoder_test.go b/plumbing/format/diff/unified_encoder_test.go
index 1a9b2dd..f72424a 100644
--- a/plumbing/format/diff/unified_encoder_test.go
+++ b/plumbing/format/diff/unified_encoder_test.go
@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"testing"
 
+	"github.com/go-git/go-git/v5/internal/color"
 	"github.com/go-git/go-git/v5/plumbing"
 	"github.com/go-git/go-git/v5/plumbing/filemode"
 
@@ -56,7 +57,7 @@ func (s *UnifiedEncoderTestSuite) TestEncode(c *C) {
 		c.Log("executing: ", f.desc)
 
 		buffer := bytes.NewBuffer(nil)
-		e := NewUnifiedEncoder(buffer, f.context)
+		e := NewUnifiedEncoder(buffer, f.context).SetColor(f.color)
 
 		err := e.Encode(f.patch)
 		c.Assert(err, IsNil)
@@ -860,6 +861,82 @@ index 0adddcde4fd38042c354518351820eb06c417c82..d39ae38aad7ba9447b5e7998b2e4714f
 +Y
 \ No newline at end of file
 `,
+}, {
+	patch: testPatch{
+		message: "",
+		filePatches: []testFilePatch{{
+			from: &testFile{
+				mode: filemode.Regular,
+				path: "README.md",
+				seed: "hello\nworld\n",
+			},
+			to: &testFile{
+				mode: filemode.Regular,
+				path: "README.md",
+				seed: "hello\nbug\n",
+			},
+			chunks: []testChunk{{
+				content: "hello\n",
+				op:      Equal,
+			}, {
+				content: "world\n",
+				op:      Delete,
+			}, {
+				content: "bug\n",
+				op:      Add,
+			}},
+		}},
+	},
+	desc:    "positive negative number with color",
+	context: 2,
+	color:   NewColorConfig(),
+	diff: "" +
+		color.Bold + "diff --git a/README.md b/README.md\n" +
+		"index 94954abda49de8615a048f8d2e64b5de848e27a1..f3dad9514629b9ff9136283ae331ad1fc95748a8 100644\n" +
+		"--- a/README.md\n" +
+		"+++ b/README.md\n" +
+		color.Reset + color.Cyan + "@@ -1,2 +1,2 @@\n" +
+		color.Normal + color.Reset + " hello\n" +
+		color.Reset + color.Red + "-world\n" +
+		color.Reset + color.Green + "+bug\n" +
+		color.Reset,
+}, {
+	patch: testPatch{
+		message: "",
+		filePatches: []testFilePatch{{
+			from: &testFile{
+				mode: filemode.Regular,
+				path: "test.txt",
+				seed: "test\n",
+			},
+			to: &testFile{
+				mode: filemode.Regular,
+				path: "test.txt",
+				seed: "test2\n",
+			},
+
+			chunks: []testChunk{{
+				content: "test\n",
+				op:      Delete,
+			}, {
+				content: "test2\n",
+				op:      Add,
+			}},
+		}},
+	},
+
+	desc:    "one line change with color",
+	context: 1,
+	color:   NewColorConfig(),
+	diff: "" +
+		color.Bold + "diff --git a/test.txt b/test.txt\n" +
+		"index 9daeafb9864cf43055ae93beb0afd6c7d144bfa4..180cf8328022becee9aaa2577a8f84ea2b9f3827 100644\n" +
+		"--- a/test.txt\n" +
+		"+++ b/test.txt\n" +
+		color.Reset + color.Cyan + "@@ -1 +1 @@\n" +
+		color.Reset + color.Red + "-test\n" +
+		color.Reset + color.Green + "+test2\n" +
+		color.Reset,
 }}
 
 type testPatch struct {
@@ -944,6 +1021,7 @@ func (t testChunk) Type() Operation {
 type fixture struct {
 	desc    string
 	context int
+	color   ColorConfig
 	diff    string
 	patch   Patch
 }