Fix range select -> stage failure when deleted file is already staged (#3631)

- **PR Description**

Fix range select -> stage failure when deleted file is already staged.

Fixes https://github.com/jesseduffield/lazygit/issues/3603

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

* [ ] 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)
* [ ] Text is internationalised (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#internationalisation))
* [ ] Docs have been updated if necessary
* [x] You've read through your own file changes for silly mistakes etc

<!--
Be sure to name your PR with an imperative e.g. 'Add worktrees view'
see https://github.com/jesseduffield/lazygit/releases/tag/v0.40.0 for
examples
-->

pkg/gui/controllers/files_controller.go

@@ -401,16 +401,18 @@ func (self *FilesController) pressWithLock(selectedNodes []*filetree.FileNode) e
 
 	selectedNodes = normalisedSelectedNodes(selectedNodes)
 
-	// If any node has unstaged changes, we'll stage all the selected nodes. Otherwise,
-	// we unstage all the selected nodes.
-	if someNodesHaveUnstagedChanges(selectedNodes) {
+	// If any node has unstaged changes, we'll stage all the selected unstaged nodes (staging already staged deleted files/folders would fail).
+	// Otherwise, we unstage all the selected nodes.
+	unstagedSelectedNodes := filterNodesHaveUnstagedChanges(selectedNodes)
+
+	if len(unstagedSelectedNodes) > 0 {
 		self.c.LogAction(self.c.Tr.Actions.StageFile)
 
-		if err := self.optimisticChange(selectedNodes, self.optimisticStage); err != nil {
+		if err := self.optimisticChange(unstagedSelectedNodes, self.optimisticStage); err != nil {
 			return err
 		}
 
-		if err := self.c.Git().WorkingTree.StageFiles(toPaths(selectedNodes)); err != nil {
+		if err := self.c.Git().WorkingTree.StageFiles(toPaths(unstagedSelectedNodes)); err != nil {
 			return err
 		}
 	} else {
@@ -1031,6 +1033,12 @@ func someNodesHaveStagedChanges(nodes []*filetree.FileNode) bool {
 	return lo.SomeBy(nodes, (*filetree.FileNode).GetHasStagedChanges)
 }
 
+func filterNodesHaveUnstagedChanges(nodes []*filetree.FileNode) []*filetree.FileNode {
+	return lo.Filter(nodes, func(node *filetree.FileNode, _ int) bool {
+		return node.GetHasUnstagedChanges()
+	})
+}
+
 func (self *FilesController) canRemove(selectedNodes []*filetree.FileNode) *types.DisabledReason {
 	submodules := self.c.Model().Submodules
 	submoduleCount := lo.CountBy(selectedNodes, func(node *filetree.FileNode) bool {

pkg/integration/tests/file/stage_deleted_range_select.go

@@ -0,0 +1,50 @@
+package file
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var StageDeletedRangeSelect = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Stage a range of deleted files using range select",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig: func(config *config.AppConfig) {
+	},
+	SetupRepo: func(shell *Shell) {
+		shell.CreateFileAndAdd("file-a", "")
+		shell.CreateFileAndAdd("file-b", "")
+		shell.Commit("first commit")
+
+		shell.DeleteFile("file-a")
+		shell.DeleteFile("file-b")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Files().
+			IsFocused().
+			Lines(
+				Contains(" D").Contains("file-a").IsSelected(),
+				Contains(" D").Contains("file-b"),
+			).
+			// Stage a single deleted file
+			PressPrimaryAction().
+			Lines(
+				Contains("D ").Contains("file-a").IsSelected(),
+				Contains(" D").Contains("file-b"),
+			).
+			Press(keys.Universal.ToggleRangeSelect).
+			NavigateToLine(Contains("file-b")).
+			// Stage both files while a deleted file is already staged
+			PressPrimaryAction().
+			Lines(
+				Contains("D ").Contains("file-a").IsSelected(),
+				Contains("D ").Contains("file-b").IsSelected(),
+			).
+			// Unstage; back to everything being unstaged
+			PressPrimaryAction().
+			Lines(
+				Contains(" D").Contains("file-a").IsSelected(),
+				Contains(" D").Contains("file-b").IsSelected(),
+			)
+	},
+})

pkg/integration/tests/test_list.go

@@ -163,6 +163,7 @@ var tests = []*components.IntegrationTest{
 	file.RememberCommitMessageAfterFail,
 	file.RenameSimilarityThresholdChange,
 	file.StageChildrenRangeSelect,
+	file.StageDeletedRangeSelect,
 	file.StageRangeSelect,
 	filter_and_search.FilterCommitFiles,
 	filter_and_search.FilterFiles,