Fix: Fixed errors that occurred with shortcut items in git repositories

[marcofranzen99]

Resolved / Related Issues

• Closes Bug: Selecting a shortcut in a git folder crashes Files #17008

Description
The problem was that GitShortcutItem cannot be cast to ShortcutItem because GitShortcutItem only inherits from GitItem and IShortcutItem. It cannot additionally inherit from ShortcutItem, since a class in C# cannot have multiple base classes.

Simply casting to IShortcutItem everywhere did not work, as the IShortcutItem interface would lack properties of the ListedItem (such as ItemPath).

That's why I decided to create an interface IListedItem. IShortcutItem & IGitItem now both inherit from this interface.

Problems only occurred with shortcut items that are part of a git repository. Not all of them led to a crash, some only displayed error messages or led to incorrect behavior. Here is a list of affected actions:

• Selecting a shortcut item
• Selecting a shortcut item with preview pane open
• Open Properties Window for a shortcut item
• Save modified properties of a shortcut via properties window
• Open in new tab
• Open in new pane
• Open in new Window
• Pin To Start
• Unpin From Start
• Share Item

Steps used to test these changes

1. tested if the actions listed above work correctly