Bundle the reverse and keepOriginalHeader flags into a PatchOptions struct

We are going to add one more flag in the next commit.

Note that we are not using the struct inside patch_manager.go; we keep passing
the individual flags there. The reason for this will become more obvious later
in this branch.

pkg/commands/patch/patch_manager.go

@@ -176,7 +176,8 @@ func (p *PatchManager) renderPlainPatchForFile(filename string, reverse bool, ke
 		return info.diff
 	case PART:
 		// generate a new diff with just the selected lines
-		return ModifiedPatchForLines(p.Log, filename, info.diff, info.includedLineIndices, reverse, keepOriginalHeader)
+		return ModifiedPatchForLines(p.Log, filename, info.diff, info.includedLineIndices,
+			PatchOptions{Reverse: reverse, KeepOriginalHeader: keepOriginalHeader})
 	default:
 		return ""
 	}

pkg/commands/patch/patch_modifier.go

@@ -13,6 +13,16 @@ var (
 	patchHeaderRegexp = regexp.MustCompile(`(?ms)(^diff.*?)^@@`)
 )
 
+type PatchOptions struct {
+	// Create a reverse patch; in other words, flip all the '+' and '-' while
+	// generating the patch.
+	Reverse bool
+
+	// Whether to keep or discard the original diff header including the
+	// "index deadbeef..fa1afe1 100644" line.
+	KeepOriginalHeader bool
+}
+
 func GetHeaderFromDiff(diff string) string {
 	match := patchHeaderRegexp.FindStringSubmatch(diff)
 	if len(match) <= 1 {
@@ -76,7 +86,7 @@ func NewPatchModifier(log *logrus.Entry, filename string, diffText string) *Patc
 	}
 }
 
-func (d *PatchModifier) ModifiedPatchForLines(lineIndices []int, reverse bool, keepOriginalHeader bool) string {
+func (d *PatchModifier) ModifiedPatchForLines(lineIndices []int, opts PatchOptions) string {
 	// step one is getting only those hunks which we care about
 	hunksInRange := []*PatchHunk{}
 outer:
@@ -95,7 +105,7 @@ outer:
 	formattedHunks := ""
 	var formattedHunk string
 	for _, hunk := range hunksInRange {
-		startOffset, formattedHunk = hunk.formatWithChanges(lineIndices, reverse, startOffset)
+		startOffset, formattedHunk = hunk.formatWithChanges(lineIndices, opts.Reverse, startOffset)
 		formattedHunks += formattedHunk
 	}
 
@@ -108,7 +118,7 @@ outer:
 	// it makes git confused e.g. when dealing with deleted/added files
 	// but with building and applying patches the original header gives git
 	// information it needs to cleanly apply patches
-	if keepOriginalHeader {
+	if opts.KeepOriginalHeader {
 		fileHeader = d.header
 	} else {
 		fileHeader = fmt.Sprintf("--- a/%s\n+++ b/%s\n", d.filename, d.filename)
@@ -117,13 +127,13 @@ outer:
 	return fileHeader + formattedHunks
 }
 
-func (d *PatchModifier) ModifiedPatchForRange(firstLineIdx int, lastLineIdx int, reverse bool, keepOriginalHeader bool) string {
+func (d *PatchModifier) ModifiedPatchForRange(firstLineIdx int, lastLineIdx int, opts PatchOptions) string {
 	// generate array of consecutive line indices from our range
 	selectedLines := []int{}
 	for i := firstLineIdx; i <= lastLineIdx; i++ {
 		selectedLines = append(selectedLines, i)
 	}
-	return d.ModifiedPatchForLines(selectedLines, reverse, keepOriginalHeader)
+	return d.ModifiedPatchForLines(selectedLines, opts)
 }
 
 func (d *PatchModifier) OriginalPatchLength() int {
@@ -134,14 +144,14 @@ func (d *PatchModifier) OriginalPatchLength() int {
 	return d.hunks[len(d.hunks)-1].LastLineIdx()
 }
 
-func ModifiedPatchForRange(log *logrus.Entry, filename string, diffText string, firstLineIdx int, lastLineIdx int, reverse bool, keepOriginalHeader bool) string {
+func ModifiedPatchForRange(log *logrus.Entry, filename string, diffText string, firstLineIdx int, lastLineIdx int, opts PatchOptions) string {
 	p := NewPatchModifier(log, filename, diffText)
-	return p.ModifiedPatchForRange(firstLineIdx, lastLineIdx, reverse, keepOriginalHeader)
+	return p.ModifiedPatchForRange(firstLineIdx, lastLineIdx, opts)
 }
 
-func ModifiedPatchForLines(log *logrus.Entry, filename string, diffText string, includedLineIndices []int, reverse bool, keepOriginalHeader bool) string {
+func ModifiedPatchForLines(log *logrus.Entry, filename string, diffText string, includedLineIndices []int, opts PatchOptions) string {
 	p := NewPatchModifier(log, filename, diffText)
-	return p.ModifiedPatchForLines(includedLineIndices, reverse, keepOriginalHeader)
+	return p.ModifiedPatchForLines(includedLineIndices, opts)
 }
 
 // I want to know, given a hunk, what line a given index is on

pkg/commands/patch/patch_modifier_test.go

@@ -513,7 +513,8 @@ func TestModifyPatchForRange(t *testing.T) {
 	for _, s := range scenarios {
 		s := s
 		t.Run(s.testName, func(t *testing.T) {
-			result := ModifiedPatchForRange(nil, s.filename, s.diffText, s.firstLineIndex, s.lastLineIndex, s.reverse, false)
+			result := ModifiedPatchForRange(nil, s.filename, s.diffText, s.firstLineIndex, s.lastLineIndex,
+				PatchOptions{Reverse: s.reverse, KeepOriginalHeader: false})
 			if !assert.Equal(t, s.expected, result) {
 				fmt.Println(result)
 			}

pkg/gui/controllers/staging_controller.go

@@ -181,7 +181,8 @@ func (self *StagingController) applySelection(reverse bool) error {
 	}
 
 	firstLineIdx, lastLineIdx := state.SelectedRange()
-	patch := patch.ModifiedPatchForRange(self.c.Log, path, state.GetDiff(), firstLineIdx, lastLineIdx, reverse, false)
+	patch := patch.ModifiedPatchForRange(self.c.Log, path, state.GetDiff(), firstLineIdx, lastLineIdx,
+		patch.PatchOptions{Reverse: reverse, KeepOriginalHeader: false})
 
 	if patch == "" {
 		return nil
@@ -227,7 +228,8 @@ func (self *StagingController) editHunk() error {
 
 	hunk := state.CurrentHunk()
 	patchText := patch.ModifiedPatchForRange(
-		self.c.Log, path, state.GetDiff(), hunk.FirstLineIdx, hunk.LastLineIdx(), self.staged, false,
+		self.c.Log, path, state.GetDiff(), hunk.FirstLineIdx, hunk.LastLineIdx(),
+		patch.PatchOptions{Reverse: self.staged, KeepOriginalHeader: false},
 	)
 	patchFilepath, err := self.git.WorkingTree.SaveTemporaryPatch(patchText)
 	if err != nil {
@@ -249,7 +251,8 @@ func (self *StagingController) editHunk() error {
 
 	lineCount := strings.Count(editedPatchText, "\n") + 1
 	newPatchText := patch.ModifiedPatchForRange(
-		self.c.Log, path, editedPatchText, 0, lineCount, false, false,
+		self.c.Log, path, editedPatchText, 0, lineCount,
+		patch.PatchOptions{Reverse: false, KeepOriginalHeader: false},
 	)
 	if err := self.git.WorkingTree.ApplyPatch(newPatchText, "cached"); err != nil {
 		return self.c.Error(err)