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/controllers/list_controller_trait.go

@@ -6,20 +6,23 @@ import "github.com/jesseduffield/lazygit/pkg/gui/types"
 // ensuring a single item is selected, etc.
 
 type ListControllerTrait[T comparable] struct {
-	c           *ControllerCommon
-	context     types.IListContext
-	getSelected func() T
+	c                *ControllerCommon
+	context          types.IListContext
+	getSelectedItem  func() T
+	getSelectedItems func() ([]T, int, int)
 }
 
 func NewListControllerTrait[T comparable](
 	c *ControllerCommon,
 	context types.IListContext,
 	getSelected func() T,
+	getSelectedItems func() ([]T, int, int),
 ) *ListControllerTrait[T] {
 	return &ListControllerTrait[T]{
-		c:           c,
-		context:     context,
-		getSelected: getSelected,
+		c:                c,
+		context:          context,
+		getSelectedItem:  getSelected,
+		getSelectedItems: getSelectedItems,
 	}
 }
 
@@ -47,7 +50,7 @@ func (self *ListControllerTrait[T]) singleItemSelected(callbacks ...func(T) *typ
 		}
 
 		var zeroValue T
-		item := self.getSelected()
+		item := self.getSelectedItem()
 		if item == zeroValue {
 			return &types.DisabledReason{Text: self.c.Tr.NoItemSelected}
 		}
@@ -62,11 +65,46 @@ func (self *ListControllerTrait[T]) singleItemSelected(callbacks ...func(T) *typ
 	}
 }
 
+// Ensures that at least one item is selected.
+func (self *ListControllerTrait[T]) itemRangeSelected(callbacks ...func([]T, int, int) *types.DisabledReason) func() *types.DisabledReason {
+	return func() *types.DisabledReason {
+		items, startIdx, endIdx := self.getSelectedItems()
+		if len(items) == 0 {
+			return &types.DisabledReason{Text: self.c.Tr.NoItemSelected}
+		}
+
+		for _, callback := range callbacks {
+			if reason := callback(items, startIdx, endIdx); reason != nil {
+				return reason
+			}
+		}
+
+		return nil
+	}
+}
+
+func (self *ListControllerTrait[T]) itemsSelected(callbacks ...func([]T) *types.DisabledReason) func() *types.DisabledReason { //nolint:unused
+	return func() *types.DisabledReason {
+		items, _, _ := self.getSelectedItems()
+		if len(items) == 0 {
+			return &types.DisabledReason{Text: self.c.Tr.NoItemSelected}
+		}
+
+		for _, callback := range callbacks {
+			if reason := callback(items); reason != nil {
+				return reason
+			}
+		}
+
+		return nil
+	}
+}
+
 // Passes the selected item to the callback. Used for handler functions.
 func (self *ListControllerTrait[T]) withItem(callback func(T) error) func() error {
 	return func() error {
 		var zeroValue T
-		commit := self.getSelected()
+		commit := self.getSelectedItem()
 		if commit == zeroValue {
 			return self.c.ErrorMsg(self.c.Tr.NoItemSelected)
 		}
@@ -75,12 +113,35 @@ func (self *ListControllerTrait[T]) withItem(callback func(T) error) func() erro
 	}
 }
 
+func (self *ListControllerTrait[T]) withItems(callback func([]T) error) func() error {
+	return func() error {
+		items, _, _ := self.getSelectedItems()
+		if len(items) == 0 {
+			return self.c.ErrorMsg(self.c.Tr.NoItemSelected)
+		}
+
+		return callback(items)
+	}
+}
+
+// like withItems but also passes the start and end index of the selection
+func (self *ListControllerTrait[T]) withItemsRange(callback func([]T, int, int) error) func() error {
+	return func() error {
+		items, startIdx, endIdx := self.getSelectedItems()
+		if len(items) == 0 {
+			return self.c.ErrorMsg(self.c.Tr.NoItemSelected)
+		}
+
+		return callback(items, startIdx, endIdx)
+	}
+}
+
 // Like withItem, but doesn't show an error message if no item is selected.
 // Use this for click actions (it's a no-op to click empty space)
 func (self *ListControllerTrait[T]) withItemGraceful(callback func(T) error) func() error {
 	return func() error {
 		var zeroValue T
-		commit := self.getSelected()
+		commit := self.getSelectedItem()
 		if commit == zeroValue {
 			return nil
 		}