Retain commit message when cycling history

When cycling history, we want to make it so that upon returning to the original prompt, you get your text back.
Importantly, we don't want to use the existing preservedMessage field for that because that's only for preserving
a NEW commit message, and we don't want the history stuff of the commit reword flow to overwrite that.

pkg/gui/context/commit_message_context.go

@@ -26,6 +26,12 @@ type CommitMessageViewModel struct {
 	preservedMessage string
 	// invoked when pressing enter in the commit message panel
 	onConfirm func(string) error
+
+	// The message typed in before cycling through history
+	// We store this separately to 'preservedMessage' because 'preservedMessage'
+	// is specifically for committing staged files and we don't want this affected
+	// by cycling through history in the context of rewording an old commit.
+	historyMessage string
 }
 
 func NewCommitMessageContext(
@@ -61,6 +67,22 @@ func (self *CommitMessageContext) GetPreserveMessage() bool {
 	return self.viewModel.preserveMessage
 }
 
+func (self *CommitMessageContext) GetPreservedMessage() string {
+	return self.viewModel.preservedMessage
+}
+
+func (self *CommitMessageContext) SetPreservedMessage(message string) {
+	self.viewModel.preservedMessage = message
+}
+
+func (self *CommitMessageContext) GetHistoryMessage() string {
+	return self.viewModel.historyMessage
+}
+
+func (self *CommitMessageContext) SetHistoryMessage(message string) {
+	self.viewModel.historyMessage = message
+}
+
 func (self *CommitMessageContext) OnConfirm(message string) error {
 	return self.viewModel.onConfirm(message)
 }
@@ -71,11 +93,3 @@ func (self *CommitMessageContext) SetPanelState(index int, title string, preserv
 	self.viewModel.onConfirm = onConfirm
 	self.GetView().Title = title
 }
-
-func (self *CommitMessageContext) SetPreservedMessage(message string) {
-	self.viewModel.preservedMessage = message
-}
-
-func (self *CommitMessageContext) GetPreservedMessage() string {
-	return self.viewModel.preservedMessage
-}