Toggle only added/deleted lines in patch building view

This improves the experience when selecting a hunk generously with the mouse, by
dragging over it including some context lines above and below. Previously we
would consider the "moving end" of the selection range for whether things need
to be added or removed, but this doesn't make sense if it's a context line. Now
we consider the first actual change line that is included in the range.

pkg/commands/patch/patch_builder.go

@@ -124,14 +124,6 @@ func (p *PatchBuilder) RemoveFile(filename string) error {
 	return nil
 }
 
-func getIndicesForRange(first, last int) []int {
-	indices := []int{}
-	for i := first; i <= last; i++ {
-		indices = append(indices, i)
-	}
-	return indices
-}
-
 func (p *PatchBuilder) getFileInfo(filename string) (*fileInfo, error) {
 	info, ok := p.fileInfoMap[filename]
 	if ok {
@@ -152,24 +144,24 @@ func (p *PatchBuilder) getFileInfo(filename string) (*fileInfo, error) {
 	return info, nil
 }
 
-func (p *PatchBuilder) AddFileLineRange(filename string, firstLineIdx, lastLineIdx int) error {
+func (p *PatchBuilder) AddFileLineRange(filename string, lineIndices []int) error {
 	info, err := p.getFileInfo(filename)
 	if err != nil {
 		return err
 	}
 	info.mode = PART
-	info.includedLineIndices = lo.Union(info.includedLineIndices, getIndicesForRange(firstLineIdx, lastLineIdx))
+	info.includedLineIndices = lo.Union(info.includedLineIndices, lineIndices)
 
 	return nil
 }
 
-func (p *PatchBuilder) RemoveFileLineRange(filename string, firstLineIdx, lastLineIdx int) error {
+func (p *PatchBuilder) RemoveFileLineRange(filename string, lineIndices []int) error {
 	info, err := p.getFileInfo(filename)
 	if err != nil {
 		return err
 	}
 	info.mode = PART
-	info.includedLineIndices, _ = lo.Difference(info.includedLineIndices, getIndicesForRange(firstLineIdx, lastLineIdx))
+	info.includedLineIndices, _ = lo.Difference(info.includedLineIndices, lineIndices)
 	if len(info.includedLineIndices) == 0 {
 		p.removeFile(info)
 	}

pkg/gui/controllers/patch_building_controller.go

@@ -126,7 +126,6 @@ func (self *PatchBuildingController) toggleSelection() error {
 	self.context().GetMutex().Lock()
 	defer self.context().GetMutex().Unlock()
 
-	toggleFunc := self.c.Git().Patch.PatchBuilder.AddFileLineRange
 	filename := self.c.Contexts().CommitFiles.GetSelectedPath()
 	if filename == "" {
 		return nil
@@ -134,19 +133,26 @@ func (self *PatchBuildingController) toggleSelection() error {
 
 	state := self.context().GetState()
 
+	// Get added/deleted lines in the selected patch range
+	lineIndicesToToggle := state.ChangeLinesInSelectedPatchRange()
+	if len(lineIndicesToToggle) == 0 {
+		// Only context lines or header lines selected, so nothing to do
+		return nil
+	}
+
 	includedLineIndices, err := self.c.Git().Patch.PatchBuilder.GetFileIncLineIndices(filename)
 	if err != nil {
 		return err
 	}
-	currentLineIsStaged := lo.Contains(includedLineIndices, state.GetSelectedPatchLineIdx())
+
-	if currentLineIsStaged {
+	toggleFunc := self.c.Git().Patch.PatchBuilder.AddFileLineRange
+	firstSelectedChangeLineIsStaged := lo.Contains(includedLineIndices, lineIndicesToToggle[0])
+	if firstSelectedChangeLineIsStaged {
 		toggleFunc = self.c.Git().Patch.PatchBuilder.RemoveFileLineRange
 	}
 
 	// add range of lines to those set for the file
-	firstLineIdx, lastLineIdx := state.SelectedPatchRange()
+	if err := toggleFunc(filename, lineIndicesToToggle); err != nil {
-
-	if err := toggleFunc(filename, firstLineIdx, lastLineIdx); err != nil {
 		// might actually want to return an error here
 		self.c.Log.Error(err)
 	}

pkg/gui/patch_exploring/state.go

@@ -282,6 +282,20 @@ func (s *State) SelectedPatchRange() (int, int) {
 	return s.patchLineIndices[start], s.patchLineIndices[end]
 }
 
+// Returns the line indices of the selected patch range that are changes (i.e. additions or deletions)
+func (s *State) ChangeLinesInSelectedPatchRange() []int {
+	viewStart, viewEnd := s.SelectedViewRange()
+	patchStart, patchEnd := s.patchLineIndices[viewStart], s.patchLineIndices[viewEnd]
+	lines := s.patch.Lines()
+	indices := []int{}
+	for i := patchStart; i <= patchEnd; i++ {
+		if lines[i].IsChange() {
+			indices = append(indices, i)
+		}
+	}
+	return indices
+}
+
 func (s *State) CurrentLineNumber() int {
 	return s.patch.LineNumberOfLine(s.patchLineIndices[s.selectedLineIdx])
 }