Split commit message panel into commit summary and commit description panel

When we use the one panel for the entire commit message, its tricky to have a keybinding both for adding a newline and submitting.
By having two panels: one for the summary line and one for the description, we allow for 'enter' to submit the message when done from the summary panel,
and 'enter' to add a newline when done from the description panel. Alt-enter, for those who can use that key combo, also works for submitting the message
from the description panel. For those who can't use that key combo, and don't want to remap the keybinding, they can hit tab to go back to the summary panel
and then 'enter' to submit the message.

We have some awkwardness in that both contexts (i.e. panels) need to appear and disappear in tandem and we don't have a great way of handling that concept,
so we just push both contexts one after the other, and likewise remove both contexts when we escape.

pkg/gui/controllers/commit_message_controller.go

@@ -1,6 +1,7 @@
 package controllers
 
 import (
+	"github.com/jesseduffield/lazygit/pkg/commands/git_commands"
 	"github.com/jesseduffield/lazygit/pkg/gui/context"
 	"github.com/jesseduffield/lazygit/pkg/gui/types"
 )
@@ -8,27 +9,16 @@ import (
 type CommitMessageController struct {
 	baseController
 	c *ControllerCommon
-
-	getCommitMessage func() string
-	onCommitAttempt  func(message string)
-	onCommitSuccess  func()
 }
 
 var _ types.IController = &CommitMessageController{}
 
 func NewCommitMessageController(
 	common *ControllerCommon,
-	getCommitMessage func() string,
-	onCommitAttempt func(message string),
-	onCommitSuccess func(),
 ) *CommitMessageController {
 	return &CommitMessageController{
 		baseController: baseController{},
 		c:              common,
-
-		getCommitMessage: getCommitMessage,
-		onCommitAttempt:  onCommitAttempt,
-		onCommitSuccess:  onCommitSuccess,
 	}
 }
 
@@ -46,6 +36,18 @@ func (self *CommitMessageController) GetKeybindings(opts types.KeybindingsOpts)
 			Handler:     self.close,
 			Description: self.c.Tr.LcClose,
 		},
+		{
+			Key:     opts.GetKey(opts.Config.Universal.PrevItem),
+			Handler: self.handlePreviousCommit,
+		},
+		{
+			Key:     opts.GetKey(opts.Config.Universal.NextItem),
+			Handler: self.handleNextCommit,
+		},
+		{
+			Key:     opts.GetKey(opts.Config.Universal.TogglePanel),
+			Handler: self.switchToCommitDescription,
+		},
 	}
 
 	return bindings
@@ -62,30 +64,61 @@ func (self *CommitMessageController) Context() types.Context {
 	return self.context()
 }
 
-// this method is pointless in this context but I'm keeping it consistent
-// with other contexts so that when generics arrive it's easier to refactor
 func (self *CommitMessageController) context() *context.CommitMessageContext {
 	return self.c.Contexts().CommitMessage
 }
 
-func (self *CommitMessageController) confirm() error {
-	message := self.getCommitMessage()
-	self.onCommitAttempt(message)
+func (self *CommitMessageController) handlePreviousCommit() error {
+	return self.handleCommitIndexChange(1)
+}
 
-	if message == "" {
-		return self.c.ErrorMsg(self.c.Tr.CommitWithoutMessageErr)
+func (self *CommitMessageController) handleNextCommit() error {
+	if self.context().GetSelectedIndex() == context.NoCommitIndex {
+		return nil
+	}
+	return self.handleCommitIndexChange(-1)
+}
+
+func (self *CommitMessageController) switchToCommitDescription() error {
+	if err := self.c.PushContext(self.c.Contexts().CommitDescription); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (self *CommitMessageController) handleCommitIndexChange(value int) error {
+	currentIndex := self.context().GetSelectedIndex()
+	newIndex := currentIndex + value
+	if newIndex == context.NoCommitIndex {
+		self.context().SetSelectedIndex(newIndex)
+		self.c.Helpers().Commits.SetMessageAndDescriptionInView("")
+		return nil
 	}
 
-	cmdObj := self.c.Git().Commit.CommitCmdObj(message)
-	self.c.LogAction(self.c.Tr.Actions.Commit)
+	validCommit, err := self.setCommitMessageAtIndex(newIndex)
+	if validCommit {
+		self.context().SetSelectedIndex(newIndex)
+	}
+	return err
+}
 
-	_ = self.c.PopContext()
-	return self.c.Helpers().GPG.WithGpgHandling(cmdObj, self.c.Tr.CommittingStatus, func() error {
-		self.onCommitSuccess()
-		return nil
-	})
+// returns true if the given index is for a valid commit
+func (self *CommitMessageController) setCommitMessageAtIndex(index int) (bool, error) {
+	commitMessage, err := self.c.Git().Commit.GetCommitMessageFromHistory(index)
+	if err != nil {
+		if err == git_commands.ErrInvalidCommitIndex {
+			return false, nil
+		}
+		return false, self.c.ErrorMsg(self.c.Tr.CommitWithoutMessageErr)
+	}
+	self.c.Helpers().Commits.UpdateCommitPanelView(commitMessage)
+	return true, nil
+}
+
+func (self *CommitMessageController) confirm() error {
+	return self.c.Helpers().Commits.HandleCommitConfirm()
 }
 
 func (self *CommitMessageController) close() error {
-	return self.c.PopContext()
+	return self.c.Helpers().Commits.CloseCommitMessagePanel()
 }