Set groundwork for better disabled reasons with range select

Something dumb that we're currently doing is expecting list items
to define an ID method which returns a string. We use that when copying
items to clipboard with ctrl+o and when getting a ref name for diffing.

This commit gets us a little deeper into that hole by explicitly requiring
list items to implement that method so that we can easily use the new
helper functions in list_controller_trait.go.

In future we need to just remove the whole ID thing entirely but I'm too
lazy to do that right now.

pkg/gui/context/remote_branches_context.go

@@ -4,6 +4,7 @@ import (
 	"github.com/jesseduffield/lazygit/pkg/commands/models"
 	"github.com/jesseduffield/lazygit/pkg/gui/presentation"
 	"github.com/jesseduffield/lazygit/pkg/gui/types"
+	"github.com/samber/lo"
 )
 
 type RemoteBranchesContext struct {
@@ -53,15 +54,6 @@ func NewRemoteBranchesContext(
 	}
 }
 
-func (self *RemoteBranchesContext) GetSelectedItemId() string {
-	item := self.GetSelected()
-	if item == nil {
-		return ""
-	}
-
-	return item.ID()
-}
-
 func (self *RemoteBranchesContext) GetSelectedRef() types.Ref {
 	remoteBranch := self.GetSelected()
 	if remoteBranch == nil {
@@ -70,6 +62,16 @@ func (self *RemoteBranchesContext) GetSelectedRef() types.Ref {
 	return remoteBranch
 }
 
+func (self *RemoteBranchesContext) GetSelectedRefs() ([]types.Ref, int, int) {
+	items, startIdx, endIdx := self.GetSelectedItems()
+
+	refs := lo.Map(items, func(item *models.RemoteBranch, _ int) types.Ref {
+		return item
+	})
+
+	return refs, startIdx, endIdx
+}
+
 func (self *RemoteBranchesContext) GetDiffTerminals() []string {
 	itemId := self.GetSelectedItemId()