Preserve pending commit message when closing/re-opening (#4191)

- **PR Description**
This PR allows lazygit to preserve the commit messages when the commit
popup gets closed.

While discussing the feature as part of its issue, two approaches were
taken into consideration:
- to store the commit content as part of the global state file
- to store the commit content in a special file to place inside the
`.git` folder

I opted for the second approach to avoid worrying about associating each
preserved message to the worktree it belongs to. I am happy to
reconsider this and opt for the alternative approach, but I wanted to
discuss this with the maintainers before deciding.

Note: The preserving file (`.git/LAZYGIT_PENDING_COMMIT`) is deleted
when the commit is finalized or when the commit content becomes empty.

pkg/gui/context/commit_message_context.go

@@ -1,15 +1,20 @@
 package context
 
 import (
+	"os"
+	"path/filepath"
 	"strconv"
 	"strings"
 
 	"github.com/jesseduffield/gocui"
 	"github.com/jesseduffield/lazygit/pkg/gui/keybindings"
 	"github.com/jesseduffield/lazygit/pkg/gui/types"
 	"github.com/jesseduffield/lazygit/pkg/utils"
+	"github.com/spf13/afero"
 )
 
+const PreservedCommitMessageFileName = "LAZYGIT_PENDING_COMMIT"
+
 type CommitMessageContext struct {
 	c *ContextCommon
 	types.Context
@@ -33,8 +38,6 @@ type CommitMessageViewModel struct {
 	// we remember the initial message so that we can tell whether we should preserve
 	// the message; if it's still identical to the initial message, we don't
 	initialMessage string
-	// the full preserved message (combined summary and description)
-	preservedMessage string
 	// invoked when pressing enter in the commit message panel
 	onConfirm func(string, string) error
 	// invoked when pressing the switch-to-editor key binding
@@ -75,16 +78,51 @@ func (self *CommitMessageContext) GetSelectedIndex() int {
 	return self.viewModel.selectedindex
 }
 
+func (self *CommitMessageContext) GetPreservedMessagePath() string {
+	return filepath.Join(self.c.Git().RepoPaths.WorktreeGitDirPath(), PreservedCommitMessageFileName)
+}
+
 func (self *CommitMessageContext) GetPreserveMessage() bool {
 	return self.viewModel.preserveMessage
 }
 
-func (self *CommitMessageContext) GetPreservedMessage() string {
-	return self.viewModel.preservedMessage
+func (self *CommitMessageContext) getPreservedMessage() (string, error) {
+	buf, err := afero.ReadFile(self.c.Fs, self.GetPreservedMessagePath())
+	if os.IsNotExist(err) {
+		return "", nil
+	}
+	if err != nil {
+		return "", err
+	}
+	return string(buf), nil
+}
+
+func (self *CommitMessageContext) GetPreservedMessageAndLogError() string {
+	msg, err := self.getPreservedMessage()
+	if err != nil {
+		self.c.Log.Errorf("error when retrieving persisted commit message: %v", err)
+	}
+	return msg
 }
 
-func (self *CommitMessageContext) SetPreservedMessage(message string) {
-	self.viewModel.preservedMessage = message
+func (self *CommitMessageContext) setPreservedMessage(message string) error {
+	preservedFilePath := self.GetPreservedMessagePath()
+
+	if len(message) == 0 {
+		err := self.c.Fs.Remove(preservedFilePath)
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return err
+	}
+
+	return afero.WriteFile(self.c.Fs, preservedFilePath, []byte(message), 0o644)
+}
+
+func (self *CommitMessageContext) SetPreservedMessageAndLogError(message string) {
+	if err := self.setPreservedMessage(message); err != nil {
+		self.c.Log.Errorf("error when persisting commit message: %v", err)
+	}
 }
 
 func (self *CommitMessageContext) GetInitialMessage() string {

pkg/gui/controllers/helpers/commits_helper.go

@@ -113,7 +113,7 @@ func (self *CommitsHelper) UpdateCommitPanelView(message string) {
 	}
 
 	if self.c.Contexts().CommitMessage.GetPreserveMessage() {
-		preservedMessage := self.c.Contexts().CommitMessage.GetPreservedMessage()
+		preservedMessage := self.c.Contexts().CommitMessage.GetPreservedMessageAndLogError()
 		self.SetMessageAndDescriptionInView(preservedMessage)
 		return
 	}
@@ -156,7 +156,7 @@ func (self *CommitsHelper) OpenCommitMessagePanel(opts *OpenCommitMessagePanelOp
 func (self *CommitsHelper) OnCommitSuccess() {
 	// if we have a preserved message we want to clear it on success
 	if self.c.Contexts().CommitMessage.GetPreserveMessage() {
-		self.c.Contexts().CommitMessage.SetPreservedMessage("")
+		self.c.Contexts().CommitMessage.SetPreservedMessageAndLogError("")
 	}
 }
 
@@ -179,7 +179,7 @@ func (self *CommitsHelper) CloseCommitMessagePanel() {
 	if self.c.Contexts().CommitMessage.GetPreserveMessage() {
 		message := self.JoinCommitMessageAndUnwrappedDescription()
 		if message != self.c.Contexts().CommitMessage.GetInitialMessage() {
-			self.c.Contexts().CommitMessage.SetPreservedMessage(message)
+			self.c.Contexts().CommitMessage.SetPreservedMessageAndLogError(message)
 		}
 	} else {
 		self.SetMessageAndDescriptionInView("")

pkg/gui/controllers/helpers/working_tree_helper.go

@@ -149,7 +149,7 @@ func (self *WorkingTreeHelper) HandleWIPCommitPress() error {
 }
 
 func (self *WorkingTreeHelper) HandleCommitPress() error {
-	message := self.c.Contexts().CommitMessage.GetPreservedMessage()
+	message := self.c.Contexts().CommitMessage.GetPreservedMessageAndLogError()
 
 	if message == "" {
 		commitPrefixConfig := self.commitPrefixConfigForRepo()

pkg/integration/components/commit_description_panel_driver.go

@@ -52,6 +52,11 @@ func (self *CommitDescriptionPanelDriver) AddCoAuthor(author string) *CommitDesc
 	return self
 }
 
+func (self *CommitDescriptionPanelDriver) Clear() *CommitDescriptionPanelDriver {
+	self.getViewDriver().Clear()
+	return self
+}
+
 func (self *CommitDescriptionPanelDriver) Title(expected *TextMatcher) *CommitDescriptionPanelDriver {
 	self.getViewDriver().Title(expected)
 

pkg/integration/components/commit_message_panel_driver.go

@@ -39,20 +39,7 @@ func (self *CommitMessagePanelDriver) SwitchToDescription() *CommitDescriptionPa
 }
 
 func (self *CommitMessagePanelDriver) Clear() *CommitMessagePanelDriver {
-	// clearing multiple times in case there's multiple lines
-	//  (the clear button only clears a single line at a time)
-	maxAttempts := 100
-	for i := 0; i < maxAttempts+1; i++ {
-		if self.getViewDriver().getView().Buffer() == "" {
-			break
-		}
-
-		self.t.press(ClearKey)
-		if i == maxAttempts {
-			panic("failed to clear commit message panel")
-		}
-	}
-
+	self.getViewDriver().Clear()
 	return self
 }
 

pkg/integration/components/view_driver.go

@@ -40,6 +40,24 @@ func (self *ViewDriver) Title(expected *TextMatcher) *ViewDriver {
 	return self
 }
 
+func (self *ViewDriver) Clear() *ViewDriver {
+	// clearing multiple times in case there's multiple lines
+	//  (the clear button only clears a single line at a time)
+	maxAttempts := 100
+	for i := 0; i < maxAttempts+1; i++ {
+		if self.getView().Buffer() == "" {
+			break
+		}
+
+		self.t.press(ClearKey)
+		if i == maxAttempts {
+			panic("failed to clear view buffer")
+		}
+	}
+
+	return self
+}
+
 // asserts that the view has lines matching the given matchers. One matcher must be passed for each line.
 // If you only care about the top n lines, use the TopLines method instead.
 // If you only care about a subset of lines, use the ContainsLines method instead.

pkg/integration/tests/commit/preserve_commit_message.go

@@ -28,13 +28,31 @@ var PreserveCommitMessage = NewIntegrationTest(NewIntegrationTestArgs{
 			Type("second paragraph").
 			Cancel()
 
+		t.FileSystem().PathPresent(".git/LAZYGIT_PENDING_COMMIT")
+
 		t.Views().Files().
 			IsFocused().
 			Press(keys.Files.CommitChanges)
 
 		t.ExpectPopup().CommitMessagePanel().
 			Content(Equals("my commit message")).
 			SwitchToDescription().
-			Content(Equals("first paragraph\n\nsecond paragraph"))
+			Content(Equals("first paragraph\n\nsecond paragraph")).
+			Clear().
+			SwitchToSummary().
+			Clear().
+			Cancel()
+
+		t.FileSystem().PathNotPresent(".git/LAZYGIT_PENDING_COMMIT")
+
+		t.Views().Files().
+			IsFocused().
+			Press(keys.Files.CommitChanges)
+
+		t.ExpectPopup().CommitMessagePanel().
+			Type("my new commit message").
+			Confirm()
+
+		t.FileSystem().PathNotPresent(".git/LAZYGIT_PENDING_COMMIT")
 	},
 })