Show diff for range selection in commits and sub-commits panel

In other views that show lists of commits (reflog and stash) it doesn't make
sense to show a range diff of selected entries because they don't form a linear
sequence, so we keep the previous behavior of showing the diff for the free end
of the selection range in those view.

The same applies to the commits view if the selection range includes rebasing
todos; these can have an arbitrary order, and a range diff doesn't make sense
for those.

pkg/gui/context/local_commits_context.go

@@ -128,6 +128,19 @@ func (self *LocalCommitsContext) GetSelectedRef() types.Ref {
 	return commit
 }
 
+func (self *LocalCommitsContext) GetSelectedRefRangeForDiffFiles() *types.RefRange {
+	commits, startIdx, endIdx := self.GetSelectedItems()
+	if commits == nil || startIdx == endIdx {
+		return nil
+	}
+	from := commits[len(commits)-1]
+	to := commits[0]
+	if from.IsTODO() || to.IsTODO() {
+		return nil
+	}
+	return &types.RefRange{From: from, To: to}
+}
+
 // Returns the commit hash of the selected commit, or an empty string if no
 // commit is selected
 func (self *LocalCommitsContext) GetSelectedCommitHash() string {

pkg/gui/context/sub_commits_context.go

@@ -186,6 +186,19 @@ func (self *SubCommitsContext) GetSelectedRef() types.Ref {
 	return commit
 }
 
+func (self *SubCommitsContext) GetSelectedRefRangeForDiffFiles() *types.RefRange {
+	commits, startIdx, endIdx := self.GetSelectedItems()
+	if commits == nil || startIdx == endIdx {
+		return nil
+	}
+	from := commits[len(commits)-1]
+	to := commits[0]
+	if from.Divergence != to.Divergence {
+		return nil
+	}
+	return &types.RefRange{From: from, To: to}
+}
+
 func (self *SubCommitsContext) GetCommits() []*models.Commit {
 	return self.getModel()
 }

pkg/gui/controllers/helpers/diff_helper.go

@@ -4,6 +4,7 @@ import (
 	"strings"
 
 	"github.com/jesseduffield/lazygit/pkg/commands/git_commands"
+	"github.com/jesseduffield/lazygit/pkg/commands/models"
 	"github.com/jesseduffield/lazygit/pkg/gui/context"
 	"github.com/jesseduffield/lazygit/pkg/gui/modes/diffing"
 	"github.com/jesseduffield/lazygit/pkg/gui/style"
@@ -49,6 +50,32 @@ func (self *DiffHelper) DiffArgs() []string {
 	return output
 }
 
+// Returns an update task that can be passed to RenderToMainViews to render a
+// diff for the selected commit(s). We need to pass both the selected commit
+// and the refRange for a range selection. If the refRange is nil (meaning that
+// either there's no range, or it can't be diffed for some reason), then we want
+// to fall back to rendering the diff for the single commit.
+func (self *DiffHelper) GetUpdateTaskForRenderingCommitsDiff(commit *models.Commit, refRange *types.RefRange) types.UpdateTask {
+	if refRange != nil {
+		from, to := refRange.From, refRange.To
+		args := []string{from.ParentRefName(), to.RefName(), "--stat", "-p"}
+		if self.c.GetAppState().IgnoreWhitespaceInDiffView {
+			args = append(args, "--ignore-all-space")
+		}
+		args = append(args, "--")
+		if path := self.c.Modes().Filtering.GetPath(); path != "" {
+			args = append(args, path)
+		}
+		cmdObj := self.c.Git().Diff.DiffCmdObj(args)
+		task := types.NewRunPtyTask(cmdObj.GetCmd())
+		task.Prefix = style.FgYellow.Sprintf("%s %s-%s\n\n", self.c.Tr.ShowingDiffForRange, from.ShortRefName(), to.ShortRefName())
+		return task
+	}
+
+	cmdObj := self.c.Git().Commit.ShowCmdObj(commit.Hash, self.c.Modes().Filtering.GetPath())
+	return types.NewRunPtyTask(cmdObj.GetCmd())
+}
+
 func (self *DiffHelper) ExitDiffMode() error {
 	self.c.Modes().Diffing = diffing.New()
 	return self.c.Refresh(types.RefreshOptions{Mode: types.ASYNC})

pkg/gui/controllers/local_commits_controller.go

@@ -290,8 +290,8 @@ func (self *LocalCommitsController) GetOnRenderToMain() func() error {
 				task = types.NewRenderStringTask(
 					self.c.Tr.ExecCommandHere + "\n\n" + commit.Name)
 			} else {
-				cmdObj := self.c.Git().Commit.ShowCmdObj(commit.Hash, self.c.Modes().Filtering.GetPath())
+				refRange := self.context().GetSelectedRefRangeForDiffFiles()
-				task = types.NewRunPtyTask(cmdObj.GetCmd())
+				task = self.c.Helpers().Diff.GetUpdateTaskForRenderingCommitsDiff(commit, refRange)
 			}
 
 			return self.c.RenderToMainViews(types.RefreshMainOpts{

pkg/gui/controllers/sub_commits_controller.go

@@ -46,9 +46,8 @@ func (self *SubCommitsController) GetOnRenderToMain() func() error {
 			if commit == nil {
 				task = types.NewRenderStringTask("No commits")
 			} else {
-				cmdObj := self.c.Git().Commit.ShowCmdObj(commit.Hash, self.c.Modes().Filtering.GetPath())
+				refRange := self.context().GetSelectedRefRangeForDiffFiles()
-
+				task = self.c.Helpers().Diff.GetUpdateTaskForRenderingCommitsDiff(commit, refRange)
-				task = types.NewRunPtyTask(cmdObj.GetCmd())
 			}
 
 			return self.c.RenderToMainViews(types.RefreshMainOpts{

pkg/gui/types/ref.go

@@ -7,3 +7,8 @@ type Ref interface {
 	ParentRefName() string
 	Description() string
 }
+
+type RefRange struct {
+	From Ref
+	To   Ref
+}

pkg/i18n/english.go

@@ -581,6 +581,7 @@ type TranslationSet struct {
 	OpenCommandLogMenu                    string
 	OpenCommandLogMenuTooltip             string
 	ShowingGitDiff                        string
+	ShowingDiffForRange                   string
 	CommitDiff                            string
 	CopyCommitHashToClipboard             string
 	CommitHash                            string
@@ -1569,6 +1570,7 @@ func EnglishTranslationSet() *TranslationSet {
 		OpenCommandLogMenu:                       "View command log options",
 		OpenCommandLogMenuTooltip:                "View options for the command log e.g. show/hide the command log and focus the command log.",
 		ShowingGitDiff:                           "Showing output for:",
+		ShowingDiffForRange:                      "Showing diff for range",
 		CommitDiff:                               "Commit diff",
 		CopyCommitHashToClipboard:                "Copy commit hash to clipboard",
 		CommitHash:                               "Commit hash",