Don't save deleted files (#24171)

We now treat new files that have no content as not-dirty. This fixes the
git diff view when deleted files are present.

It also fixes a long-standing bug where `zed RAEDME` and then closing
the tab would prompt for "unsaved changes" when there were none.

Release Notes:

- Fixed a bug where closing an empty, named, file would warn about
unsaved content.

crates/git_ui/src/project_diff.rs

@@ -27,7 +27,7 @@ use workspace::{
 
 use crate::git_panel::GitPanel;
 
-actions!(git, [ShowUncommittedChanges]);
+actions!(git, [Diff]);
 
 pub(crate) struct ProjectDiff {
     multibuffer: Entity<MultiBuffer>,
@@ -63,7 +63,7 @@ impl ProjectDiff {
 
     fn deploy(
         workspace: &mut Workspace,
-        _: &ShowUncommittedChanges,
+        _: &Diff,
         window: &mut Window,
         cx: &mut Context<Workspace>,
     ) {