Introduce a new /delta command (#17903)

Release Notes:

- Added a new `/delta` command to re-insert changed files that were
previously included in a context.

---------

Co-authored-by: Roy <roy@anthropic.com>

crates/assistant/src/slash_command/fetch_command.rs

@@ -11,7 +11,7 @@ use futures::AsyncReadExt;
 use gpui::{Task, WeakView};
 use html_to_markdown::{convert_html_to_markdown, markdown, TagHandler};
 use http_client::{AsyncBody, HttpClient, HttpClientWithUrl};
-use language::LspAdapterDelegate;
+use language::{BufferSnapshot, LspAdapterDelegate};
 use ui::prelude::*;
 use workspace::Workspace;
 
@@ -128,6 +128,8 @@ impl SlashCommand for FetchSlashCommand {
     fn run(
         self: Arc<Self>,
         arguments: &[String],
+        _context_slash_command_output_sections: &[SlashCommandOutputSection<language::Anchor>],
+        _context_buffer: BufferSnapshot,
         workspace: WeakView<Workspace>,
         _delegate: Option<Arc<dyn LspAdapterDelegate>>,
         cx: &mut WindowContext,
@@ -161,6 +163,7 @@ impl SlashCommand for FetchSlashCommand {
                     range,
                     icon: IconName::AtSign,
                     label: format!("fetch {}", url).into(),
+                    metadata: None,
                 }],
                 run_commands_in_text: false,
             })