Non-sticky range selection diff (#3869)

- **PR Description**

When selecting a range of commits, show the combined diff for them.

Along the way, fix a few minor issues with the current implementation of
diffing mode; see the individual commit messages for details.

Fixes #3862.

- **Please check if the PR fulfills these requirements**

* [x] Cheatsheets are up-to-date (run `go generate ./...`)
* [x] Code has been formatted (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#code-formatting))
* [x] Tests have been added/updated (see
[here](https://github.com/jesseduffield/lazygit/blob/master/pkg/integration/README.md)
for the integration test guide)
* [x] Text is internationalised (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#internationalisation))
* [ ] If a new UserConfig entry was added, make sure it can be
hot-reloaded (see
[here](https://github.com/jesseduffield/lazygit/blob/master/docs/dev/Codebase_Guide.md#using-userconfig))
* [ ] Docs have been updated if necessary
* [x] You've read through your own file changes for silly mistakes etc

pkg/commands/models/branch.go

@@ -53,6 +53,10 @@ func (b *Branch) RefName() string {
 	return b.Name
 }
 
+func (b *Branch) ShortRefName() string {
+	return b.RefName()
+}
+
 func (b *Branch) ParentRefName() string {
 	return b.RefName() + "^"
 }

pkg/commands/models/commit.go

@@ -70,6 +70,10 @@ func (c *Commit) RefName() string {
 	return c.Hash
 }
 
+func (c *Commit) ShortRefName() string {
+	return c.Hash[:7]
+}
+
 func (c *Commit) ParentRefName() string {
 	if c.IsFirstCommit() {
 		return EmptyTreeCommitHash

pkg/commands/models/remote_branch.go

@@ -18,6 +18,10 @@ func (r *RemoteBranch) RefName() string {
 	return r.FullName()
 }
 
+func (r *RemoteBranch) ShortRefName() string {
+	return r.RefName()
+}
+
 func (r *RemoteBranch) ParentRefName() string {
 	return r.RefName() + "^"
 }

pkg/commands/models/stash_entry.go

@@ -17,6 +17,10 @@ func (s *StashEntry) RefName() string {
 	return fmt.Sprintf("stash@{%d}", s.Index)
 }
 
+func (s *StashEntry) ShortRefName() string {
+	return s.RefName()
+}
+
 func (s *StashEntry) ParentRefName() string {
 	return s.RefName() + "^"
 }

pkg/commands/models/tag.go

@@ -16,6 +16,10 @@ func (t *Tag) RefName() string {
 	return t.Name
 }
 
+func (t *Tag) ShortRefName() string {
+	return t.RefName()
+}
+
 func (t *Tag) ParentRefName() string {
 	return t.RefName() + "^"
 }

pkg/gui/context/commit_files_context.go

@@ -1,6 +1,8 @@
 package context
 
 import (
+	"fmt"
+
 	"github.com/jesseduffield/gocui"
 	"github.com/jesseduffield/lazygit/pkg/commands/models"
 	"github.com/jesseduffield/lazygit/pkg/gui/filetree"
@@ -75,6 +77,25 @@ func (self *CommitFilesContext) GetDiffTerminals() []string {
 	return []string{self.GetRef().RefName()}
 }
 
+func (self *CommitFilesContext) GetFromAndToForDiff() (string, string) {
+	if refs := self.GetRefRange(); refs != nil {
+		return refs.From.ParentRefName(), refs.To.RefName()
+	}
+	ref := self.GetRef()
+	return ref.ParentRefName(), ref.RefName()
+}
+
 func (self *CommitFilesContext) ModelSearchResults(searchStr string, caseSensitive bool) []gocui.SearchPosition {
 	return nil
 }
+
+func (self *CommitFilesContext) ReInit(ref types.Ref, refRange *types.RefRange) {
+	self.SetRef(ref)
+	self.SetRefRange(refRange)
+	if refRange != nil {
+		self.SetTitleRef(fmt.Sprintf("%s-%s", refRange.From.ShortRefName(), refRange.To.ShortRefName()))
+	} else {
+		self.SetTitleRef(ref.Description())
+	}
+	self.GetView().Title = self.Title()
+}

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/reflog_commits_context.go

@@ -71,6 +71,11 @@ func (self *ReflogCommitsContext) GetSelectedRef() types.Ref {
 	return commit
 }
 
+func (self *ReflogCommitsContext) GetSelectedRefRangeForDiffFiles() *types.RefRange {
+	// It doesn't make much sense to show a range diff between two reflog entries.
+	return nil
+}
+
 func (self *ReflogCommitsContext) GetCommits() []*models.Commit {
 	return self.getModel()
 }

pkg/gui/context/stash_context.go

@@ -61,6 +61,11 @@ func (self *StashContext) GetSelectedRef() types.Ref {
 	return stash
 }
 
+func (self *StashContext) GetSelectedRefRangeForDiffFiles() *types.RefRange {
+	// It doesn't make much sense to show a range diff between two stash entries.
+	return nil
+}
+
 func (self *StashContext) GetDiffTerminals() []string {
 	itemId := self.GetSelectedItemId()
 

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.go

@@ -259,7 +259,7 @@ func (gui *Gui) resetHelpersAndControllers() {
 		gui.State.Contexts.Stash,
 	} {
 		controllers.AttachControllers(context, controllers.NewSwitchToDiffFilesController(
-			common, context, gui.State.Contexts.CommitFiles,
+			common, context,
 		))
 	}
 

pkg/gui/controllers/commits_files_controller.go

@@ -136,9 +136,8 @@ func (self *CommitFilesController) GetOnRenderToMain() func() error {
 			return nil
 		}
 
-		ref := self.context().GetRef()
-		to := ref.RefName()
-		from, reverse := self.c.Modes().Diffing.GetFromAndReverseArgsForDiff(ref.ParentRefName())
+		from, to := self.context().GetFromAndToForDiff()
+		from, reverse := self.c.Modes().Diffing.GetFromAndReverseArgsForDiff(from)
 
 		cmdObj := self.c.Git().WorkingTree.ShowFileDiffCmdObj(from, to, reverse, node.GetPath(), false)
 		task := types.NewRunPtyTask(cmdObj.GetCmd())
@@ -250,9 +249,8 @@ func (self *CommitFilesController) canEditFiles(nodes []*filetree.CommitFileNode
 }
 
 func (self *CommitFilesController) openDiffTool(node *filetree.CommitFileNode) error {
-	ref := self.context().GetRef()
-	to := ref.RefName()
-	from, reverse := self.c.Modes().Diffing.GetFromAndReverseArgsForDiff(ref.ParentRefName())
+	from, to := self.context().GetFromAndToForDiff()
+	from, reverse := self.c.Modes().Diffing.GetFromAndReverseArgsForDiff(from)
 	_, err := self.c.RunSubprocess(self.c.Git().Diff.OpenDiffToolCmdObj(
 		git_commands.DiffToolCmdOptions{
 			Filepath:    node.GetPath(),
@@ -307,7 +305,8 @@ func (self *CommitFilesController) toggleForPatch(selectedNodes []*filetree.Comm
 		})
 	}
 
-	if self.c.Git().Patch.PatchBuilder.Active() && self.c.Git().Patch.PatchBuilder.To != self.context().GetRef().RefName() {
+	from, to, reverse := self.currentFromToReverseForPatchBuilding()
+	if self.c.Git().Patch.PatchBuilder.Active() && self.c.Git().Patch.PatchBuilder.NewPatchRequired(from, to, reverse) {
 		return self.c.Confirm(types.ConfirmOpts{
 			Title:  self.c.Tr.DiscardPatch,
 			Prompt: self.c.Tr.DiscardPatchConfirm,
@@ -330,14 +329,20 @@ func (self *CommitFilesController) startPatchBuilder() error {
 	commitFilesContext := self.context()
 
 	canRebase := commitFilesContext.GetCanRebase()
-	ref := commitFilesContext.GetRef()
-	to := ref.RefName()
-	from, reverse := self.c.Modes().Diffing.GetFromAndReverseArgsForDiff(ref.ParentRefName())
+	from, to, reverse := self.currentFromToReverseForPatchBuilding()
 
 	self.c.Git().Patch.PatchBuilder.Start(from, to, reverse, canRebase)
 	return nil
 }
 
+func (self *CommitFilesController) currentFromToReverseForPatchBuilding() (string, string, bool) {
+	commitFilesContext := self.context()
+
+	from, to := commitFilesContext.GetFromAndToForDiff()
+	from, reverse := self.c.Modes().Diffing.GetFromAndReverseArgsForDiff(from)
+	return from, to, reverse
+}
+
 func (self *CommitFilesController) enter(node *filetree.CommitFileNode) error {
 	return self.enterCommitFile(node, types.OnFocusOpts{ClickedWindowName: "", ClickedViewLineIdx: -1})
 }
@@ -357,7 +362,8 @@ func (self *CommitFilesController) enterCommitFile(node *filetree.CommitFileNode
 		return self.c.Context().Push(self.c.Contexts().CustomPatchBuilder, opts)
 	}
 
-	if self.c.Git().Patch.PatchBuilder.Active() && self.c.Git().Patch.PatchBuilder.To != self.context().GetRef().RefName() {
+	from, to, reverse := self.currentFromToReverseForPatchBuilding()
+	if self.c.Git().Patch.PatchBuilder.Active() && self.c.Git().Patch.PatchBuilder.NewPatchRequired(from, to, reverse) {
 		return self.c.Confirm(types.ConfirmOpts{
 			Title:  self.c.Tr.DiscardPatch,
 			Prompt: self.c.Tr.DiscardPatchConfirm,

pkg/gui/controllers/helpers/diff_helper.go

@@ -1,9 +1,13 @@
 package helpers
 
 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"
 	"github.com/jesseduffield/lazygit/pkg/gui/types"
 	"github.com/samber/lo"
 )
@@ -19,7 +23,7 @@ func NewDiffHelper(c *HelperCommon) *DiffHelper {
 }
 
 func (self *DiffHelper) DiffArgs() []string {
-	output := []string{self.c.Modes().Diffing.Ref}
+	output := []string{"--stat", "-p", self.c.Modes().Diffing.Ref}
 
 	right := self.currentDiffTerminal()
 	if right != "" {
@@ -46,14 +50,46 @@ 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})
 }
 
 func (self *DiffHelper) RenderDiff() error {
-	cmdObj := self.c.Git().Diff.DiffCmdObj(self.DiffArgs())
+	args := self.DiffArgs()
+	cmdObj := self.c.Git().Diff.DiffCmdObj(args)
 	task := types.NewRunPtyTask(cmdObj.GetCmd())
+	task.Prefix = style.FgMagenta.Sprintf(
+		"%s %s\n\n",
+		self.c.Tr.ShowingGitDiff,
+		"git diff "+strings.Join(args, " "),
+	)
 
 	return self.c.RenderToMainViews(types.RefreshMainOpts{
 		Pair: self.c.MainViewPairs().Normal,

pkg/gui/controllers/helpers/patch_building_helper.go

@@ -73,9 +73,8 @@ func (self *PatchBuildingHelper) RefreshPatchBuildingPanel(opts types.OnFocusOpt
 		return nil
 	}
 
-	ref := self.c.Contexts().CommitFiles.CommitFileTreeViewModel.GetRef()
-	to := ref.RefName()
-	from, reverse := self.c.Modes().Diffing.GetFromAndReverseArgsForDiff(ref.ParentRefName())
+	from, to := self.c.Contexts().CommitFiles.GetFromAndToForDiff()
+	from, reverse := self.c.Modes().Diffing.GetFromAndReverseArgsForDiff(from)
 	diff, err := self.c.Git().WorkingTree.ShowFileDiff(from, to, reverse, path, true)
 	if err != nil {
 		return err

pkg/gui/controllers/helpers/refresh_helper.go

@@ -285,8 +285,8 @@ func (self *RefreshHelper) refreshCommitsAndCommitFiles() {
 		// For now the awkwardness remains.
 		commit := self.c.Contexts().LocalCommits.GetSelected()
 		if commit != nil && commit.RefName() != "" {
-			self.c.Contexts().CommitFiles.SetRef(commit)
-			self.c.Contexts().CommitFiles.SetTitleRef(commit.RefName())
+			refRange := self.c.Contexts().LocalCommits.GetSelectedRefRangeForDiffFiles()
+			self.c.Contexts().CommitFiles.ReInit(commit, refRange)
 			_ = self.refreshCommitFilesContext()
 		}
 	}
@@ -387,9 +387,8 @@ func (self *RefreshHelper) RefreshAuthors(commits []*models.Commit) {
 }
 
 func (self *RefreshHelper) refreshCommitFilesContext() error {
-	ref := self.c.Contexts().CommitFiles.GetRef()
-	to := ref.RefName()
-	from, reverse := self.c.Modes().Diffing.GetFromAndReverseArgsForDiff(ref.ParentRefName())
+	from, to := self.c.Contexts().CommitFiles.GetFromAndToForDiff()
+	from, reverse := self.c.Modes().Diffing.GetFromAndReverseArgsForDiff(from)
 
 	files, err := self.c.Git().Loaders.CommitFileLoader.GetFilesInDiff(from, to, reverse)
 	if err != nil {

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())
-				task = types.NewRunPtyTask(cmdObj.GetCmd())
+				refRange := self.context().GetSelectedRefRangeForDiffFiles()
+				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())
-
-				task = types.NewRunPtyTask(cmdObj.GetCmd())
+				refRange := self.context().GetSelectedRefRangeForDiffFiles()
+				task = self.c.Helpers().Diff.GetUpdateTaskForRenderingCommitsDiff(commit, refRange)
 			}
 
 			return self.c.RenderToMainViews(types.RefreshMainOpts{

pkg/gui/controllers/switch_to_diff_files_controller.go

@@ -1,7 +1,6 @@
 package controllers
 
 import (
-	"github.com/jesseduffield/lazygit/pkg/gui/context"
 	"github.com/jesseduffield/lazygit/pkg/gui/types"
 )
 
@@ -13,36 +12,25 @@ type CanSwitchToDiffFiles interface {
 	types.IListContext
 	CanRebase() bool
 	GetSelectedRef() types.Ref
+	GetSelectedRefRangeForDiffFiles() *types.RefRange
 }
 
-// Not using our ListControllerTrait because our 'selected' item is not a list item
-// but an attribute on it i.e. the ref of an item.
+// Not using our ListControllerTrait because we have our own way of working with
+// range selections that's different from ListControllerTrait's
 type SwitchToDiffFilesController struct {
 	baseController
-	*ListControllerTrait[types.Ref]
 	c       *ControllerCommon
 	context CanSwitchToDiffFiles
-	diffFilesContext *context.CommitFilesContext
 }
 
 func NewSwitchToDiffFilesController(
 	c *ControllerCommon,
 	context CanSwitchToDiffFiles,
-	diffFilesContext *context.CommitFilesContext,
 ) *SwitchToDiffFilesController {
 	return &SwitchToDiffFilesController{
 		baseController: baseController{},
-		ListControllerTrait: NewListControllerTrait[types.Ref](
-			c,
-			context,
-			context.GetSelectedRef,
-			func() ([]types.Ref, int, int) {
-				panic("Not implemented")
-			},
-		),
 		c:              c,
 		context:        context,
-		diffFilesContext: diffFilesContext,
 	}
 }
 
@@ -50,8 +38,8 @@ func (self *SwitchToDiffFilesController) GetKeybindings(opts types.KeybindingsOp
 	bindings := []*types.Binding{
 		{
 			Key:               opts.GetKey(opts.Config.Universal.GoInto),
-			Handler:           self.withItem(self.enter),
-			GetDisabledReason: self.require(self.singleItemSelected(self.itemRepresentsCommit)),
+			Handler:           self.enter,
+			GetDisabledReason: self.canEnter,
 			Description:       self.c.Tr.ViewItemFiles,
 		},
 	}
@@ -59,29 +47,43 @@ func (self *SwitchToDiffFilesController) GetKeybindings(opts types.KeybindingsOp
 	return bindings
 }
 
+func (self *SwitchToDiffFilesController) Context() types.Context {
+	return self.context
+}
+
 func (self *SwitchToDiffFilesController) GetOnClick() func() error {
-	return self.withItemGraceful(self.enter)
+	return func() error {
+		if self.canEnter() == nil {
+			return self.enter()
 		}
 
-func (self *SwitchToDiffFilesController) enter(ref types.Ref) error {
-	return self.viewFiles(SwitchToCommitFilesContextOpts{
-		Ref:       ref,
-		CanRebase: self.context.CanRebase(),
-		Context:   self.context,
-	})
+		return nil
+	}
 }
 
-func (self *SwitchToDiffFilesController) viewFiles(opts SwitchToCommitFilesContextOpts) error {
-	diffFilesContext := self.diffFilesContext
+func (self *SwitchToDiffFilesController) enter() error {
+	ref := self.context.GetSelectedRef()
+	refsRange := self.context.GetSelectedRefRangeForDiffFiles()
+	commitFilesContext := self.c.Contexts().CommitFiles
 
-	diffFilesContext.SetSelection(0)
-	diffFilesContext.SetRef(opts.Ref)
-	diffFilesContext.SetTitleRef(opts.Ref.Description())
-	diffFilesContext.SetCanRebase(opts.CanRebase)
-	diffFilesContext.SetParentContext(opts.Context)
-	diffFilesContext.SetWindowName(opts.Context.GetWindowName())
-	diffFilesContext.ClearSearchString()
-	diffFilesContext.GetView().TitlePrefix = opts.Context.GetView().TitlePrefix
+	canRebase := self.context.CanRebase()
+	if canRebase {
+		if self.c.Modes().Diffing.Active() {
+			if self.c.Modes().Diffing.Ref != ref.RefName() {
+				canRebase = false
+			}
+		} else if refsRange != nil {
+			canRebase = false
+		}
+	}
+
+	commitFilesContext.ReInit(ref, refsRange)
+	commitFilesContext.SetSelection(0)
+	commitFilesContext.SetCanRebase(canRebase)
+	commitFilesContext.SetParentContext(self.context)
+	commitFilesContext.SetWindowName(self.context.GetWindowName())
+	commitFilesContext.ClearSearchString()
+	commitFilesContext.GetView().TitlePrefix = self.context.GetView().TitlePrefix
 
 	if err := self.c.Refresh(types.RefreshOptions{
 		Scope: []types.RefreshableView{types.COMMIT_FILES},
@@ -89,10 +91,18 @@ func (self *SwitchToDiffFilesController) viewFiles(opts SwitchToCommitFilesConte
 		return err
 	}
 
-	return self.c.Context().Push(diffFilesContext)
+	return self.c.Context().Push(commitFilesContext)
 }
 
-func (self *SwitchToDiffFilesController) itemRepresentsCommit(ref types.Ref) *types.DisabledReason {
+func (self *SwitchToDiffFilesController) canEnter() *types.DisabledReason {
+	refRange := self.context.GetSelectedRefRangeForDiffFiles()
+	if refRange != nil {
+		return nil
+	}
+	ref := self.context.GetSelectedRef()
+	if ref == nil {
+		return &types.DisabledReason{Text: self.c.Tr.NoItemSelected}
+	}
 	if ref.RefName() == "" {
 		return &types.DisabledReason{Text: self.c.Tr.SelectedItemDoesNotHaveFiles}
 	}

pkg/gui/controllers/types.go

@@ -1,18 +0,0 @@
-package controllers
-
-import (
-	"github.com/jesseduffield/lazygit/pkg/gui/types"
-)
-
-// all fields mandatory (except `CanRebase` because it's boolean)
-type SwitchToCommitFilesContextOpts struct {
-	// this is something like a commit or branch
-	Ref types.Ref
-
-	// from the local commits view we're allowed to do rebase stuff with any patch
-	// we generate from the diff files context, but we don't have that same ability
-	// with say the sub commits context or the reflog context.
-	CanRebase bool
-
-	Context types.Context
-}

pkg/gui/filetree/commit_file_tree_view_model.go

@@ -16,6 +16,8 @@ type ICommitFileTreeViewModel interface {
 
 	GetRef() types.Ref
 	SetRef(types.Ref)
+	GetRefRange() *types.RefRange // can be nil, in which case GetRef should be used
+	SetRefRange(*types.RefRange)  // should be set to nil when selection is not a range
 	GetCanRebase() bool
 	SetCanRebase(bool)
 }
@@ -25,9 +27,14 @@ type CommitFileTreeViewModel struct {
 	types.IListCursor
 	ICommitFileTree
 
-	// this is e.g. the commit for which we're viewing the files
+	// this is e.g. the commit for which we're viewing the files, if there is no
+	// range selection, or if the range selection can't be used for some reason
 	ref types.Ref
 
+	// this is a commit range for which we're viewing the files. Can be nil, in
+	// which case ref is used.
+	refRange *types.RefRange
+
 	// we set this to true when you're viewing the files within the checked-out branch's commits.
 	// If you're viewing the files of some random other branch we can't do any rebase stuff.
 	canRebase bool
@@ -42,6 +49,7 @@ func NewCommitFileTreeViewModel(getFiles func() []*models.CommitFile, log *logru
 		ICommitFileTree: fileTree,
 		IListCursor:     listCursor,
 		ref:             nil,
+		refRange:        nil,
 		canRebase:       false,
 	}
 }
@@ -54,6 +62,14 @@ func (self *CommitFileTreeViewModel) SetRef(ref types.Ref) {
 	self.ref = ref
 }
 
+func (self *CommitFileTreeViewModel) GetRefRange() *types.RefRange {
+	return self.refRange
+}
+
+func (self *CommitFileTreeViewModel) SetRefRange(refsForRange *types.RefRange) {
+	self.refRange = refsForRange
+}
+
 func (self *CommitFileTreeViewModel) GetCanRebase() bool {
 	return self.canRebase
 }

pkg/gui/types/ref.go

@@ -3,6 +3,12 @@ package types
 type Ref interface {
 	FullRefName() string
 	RefName() string
+	ShortRefName() string
 	ParentRefName() string
 	Description() string
 }
+
+type RefRange struct {
+	From Ref
+	To   Ref
+}

pkg/i18n/english.go

@@ -445,7 +445,6 @@ type TranslationSet struct {
 	ScrollRight                           string
 	DiscardPatch                          string
 	DiscardPatchConfirm                   string
-	DiscardPatchSameCommitConfirm         string
 	CantPatchWhileRebasingError           string
 	ToggleAddToPatch                      string
 	ToggleAddToPatchTooltip               string
@@ -582,6 +581,7 @@ type TranslationSet struct {
 	OpenCommandLogMenu                    string
 	OpenCommandLogMenuTooltip             string
 	ShowingGitDiff                        string
+	ShowingDiffForRange                   string
 	CommitDiff                            string
 	CopyCommitHashToClipboard             string
 	CommitHash                            string
@@ -1435,7 +1435,6 @@ func EnglishTranslationSet() *TranslationSet {
 		ScrollRight:                          "Scroll right",
 		DiscardPatch:                         "Discard patch",
 		DiscardPatchConfirm:                  "You can only build a patch from one commit/stash-entry at a time. Discard current patch?",
-		DiscardPatchSameCommitConfirm:        "You currently have changes added to a patch for this commit. Discard current patch?",
 		CantPatchWhileRebasingError:          "You cannot build a patch or run patch commands while in a merging or rebasing state",
 		ToggleAddToPatch:                     "Toggle file included in patch",
 		ToggleAddToPatchTooltip:              "Toggle whether the file is included in the custom patch. See {{.doc}}.",
@@ -1571,6 +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",

pkg/integration/tests/diff/diff.go

@@ -35,11 +35,11 @@ var Diff = NewIntegrationTest(NewIntegrationTestArgs{
 		t.Views().Branches().
 			IsFocused().
 			Tap(func() {
-				t.Views().Information().Content(Contains("Showing output for: git diff branch-a branch-a"))
+				t.Views().Information().Content(Contains("Showing output for: git diff --stat -p branch-a branch-a"))
 			}).
 			SelectNextItem().
 			Tap(func() {
-				t.Views().Information().Content(Contains("Showing output for: git diff branch-a branch-b"))
+				t.Views().Information().Content(Contains("Showing output for: git diff --stat -p branch-a branch-b"))
 				t.Views().Main().Content(Contains("+second line"))
 			}).
 			PressEnter()
@@ -67,7 +67,7 @@ var Diff = NewIntegrationTest(NewIntegrationTestArgs{
 			Press(keys.Universal.DiffingMenu)
 
 		t.ExpectPopup().Menu().Title(Equals("Diffing")).Select(Contains("Reverse diff direction")).Confirm()
-		t.Views().Information().Content(Contains("Showing output for: git diff branch-a branch-b -R"))
+		t.Views().Information().Content(Contains("Showing output for: git diff --stat -p branch-a branch-b -R"))
 		t.Views().Main().Content(Contains("-second line"))
 	},
 })

pkg/integration/tests/diff/diff_and_apply_patch.go

@@ -32,13 +32,13 @@ var DiffAndApplyPatch = NewIntegrationTest(NewIntegrationTestArgs{
 
 		t.ExpectPopup().Menu().Title(Equals("Diffing")).Select(Equals("Diff branch-a")).Confirm()
 
-		t.Views().Information().Content(Contains("Showing output for: git diff branch-a branch-a"))
+		t.Views().Information().Content(Contains("Showing output for: git diff --stat -p branch-a branch-a"))
 
 		t.Views().Branches().
 			IsFocused().
 			SelectNextItem().
 			Tap(func() {
-				t.Views().Information().Content(Contains("Showing output for: git diff branch-a branch-b"))
+				t.Views().Information().Content(Contains("Showing output for: git diff --stat -p branch-a branch-b"))
 				t.Views().Main().Content(Contains("+second line"))
 			}).
 			PressEnter()

pkg/integration/tests/diff/diff_non_sticky_range.go

@@ -0,0 +1,45 @@
+package diff
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var DiffNonStickyRange = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "View the combined diff of multiple commits using a range selection",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.EmptyCommit("initial commit")
+		shell.CreateFileAndAdd("file1", "first line\n")
+		shell.Commit("first commit")
+		shell.UpdateFileAndAdd("file1", "first line\nsecond line\n")
+		shell.Commit("second commit")
+		shell.UpdateFileAndAdd("file1", "first line\nsecond line\nthird line\n")
+		shell.Commit("third commit")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Commits().
+			Focus().
+			Lines(
+				Contains("third commit").IsSelected(),
+				Contains("second commit"),
+				Contains("first commit"),
+				Contains("initial commit"),
+			).
+			Press(keys.Universal.RangeSelectDown).
+			Press(keys.Universal.RangeSelectDown).
+			Tap(func() {
+				t.Views().Main().Content(Contains("Showing diff for range ").
+					Contains("+first line\n+second line\n+third line"))
+			}).
+			PressEnter()
+
+		t.Views().CommitFiles().
+			IsFocused().
+			SelectedLine(Contains("file1"))
+
+		t.Views().Main().Content(Contains("+first line\n+second line\n+third line"))
+	},
+})

pkg/integration/tests/test_list.go

@@ -148,6 +148,7 @@ var tests = []*components.IntegrationTest{
 	diff.Diff,
 	diff.DiffAndApplyPatch,
 	diff.DiffCommits,
+	diff.DiffNonStickyRange,
 	diff.IgnoreWhitespace,
 	diff.RenameSimilarityThresholdChange,
 	file.CopyMenu,