Allow discarding changes only from local commits

We use CommitFilesController also for the files of commits that we show
elsewhere, e.g. for branch commits, tags, or stashes. It doesn't make sense to
discard changes from those (for stashes it might be possible to implement it
somehow, but that would be a new feature), so we disallow it unless we are in
the local commits panel.

pkg/gui/controllers/commits_files_controller.go

@@ -153,6 +153,11 @@ func (self *CommitFilesController) checkout(node *filetree.CommitFileNode) error
 }
 
 func (self *CommitFilesController) discard(node *filetree.CommitFileNode) error {
+	parentContext, ok := self.c.CurrentContext().GetParentContext()
+	if !ok || parentContext.GetKey() != context.LOCAL_COMMITS_CONTEXT_KEY {
+		return self.c.ErrorMsg(self.c.Tr.CanOnlyDiscardFromLocalCommits)
+	}
+
 	if node.File == nil {
 		return self.c.ErrorMsg(self.c.Tr.DiscardNotSupportedForDirectory)
 	}

pkg/i18n/english.go

@@ -265,6 +265,7 @@ type TranslationSet struct {
 	ViewItemFiles                       string
 	CommitFilesTitle                    string
 	CheckoutCommitFile                  string
+	CanOnlyDiscardFromLocalCommits      string
 	DiscardOldFileChange                string
 	DiscardFileChangesTitle             string
 	DiscardFileChangesPrompt            string
@@ -955,6 +956,7 @@ func EnglishTranslationSet() TranslationSet {
 		ViewItemFiles:                       "View selected item's files",
 		CommitFilesTitle:                    "Commit files",
 		CheckoutCommitFile:                  "Checkout file",
+		CanOnlyDiscardFromLocalCommits:      "Changes can only be discarded from local commits",
 		DiscardOldFileChange:                "Discard this commit's changes to this file",
 		DiscardFileChangesTitle:             "Discard file changes",
 		DiscardFileChangesPrompt:            "Are you sure you want to discard this commit's changes to this file?",

pkg/integration/tests/stash/prevent_discarding_file_changes.go

@@ -0,0 +1,41 @@
+package stash
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var PreventDiscardingFileChanges = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Check that it is not allowed to discard changes to a file of a stash",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.EmptyCommit("initial commit")
+		shell.CreateFile("file", "content")
+		shell.GitAddAll()
+		shell.Stash("stash one")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Files().IsEmpty()
+
+		t.Views().Stash().
+			Focus().
+			Lines(
+				Contains("stash one").IsSelected(),
+			).
+			PressEnter()
+
+		t.Views().CommitFiles().
+			IsFocused().
+			Lines(
+				Contains("file").IsSelected(),
+			).
+			Press(keys.Universal.Remove)
+
+		t.ExpectPopup().Confirmation().
+			Title(Equals("Error")).
+			Content(Contains("Changes can only be discarded from local commits")).
+			Confirm()
+	},
+})

pkg/integration/tests/test_list.go

@@ -155,6 +155,7 @@ var tests = []*components.IntegrationTest{
 	stash.CreateBranch,
 	stash.Drop,
 	stash.Pop,
+	stash.PreventDiscardingFileChanges,
 	stash.Rename,
 	stash.Stash,
 	stash.StashAll,