Clean up RelPath API (#38912)

Consolidate constructors and accessors.

Release Notes:

- N/A

---------

Co-authored-by: Cole Miller <cole@zed.dev>

crates/git_ui/src/commit_view.rs

@@ -128,7 +128,7 @@ impl CommitView {
         let mut metadata_buffer_id = None;
         if let Some(worktree_id) = first_worktree_id {
             let file = Arc::new(CommitMetadataFile {
-                title: RelPath::new(&format!("commit {}", commit.sha))
+                title: RelPath::unix(&format!("commit {}", commit.sha))
                     .unwrap()
                     .into(),
                 worktree_id,
@@ -145,7 +145,7 @@ impl CommitView {
             });
             multibuffer.update(cx, |multibuffer, cx| {
                 multibuffer.set_excerpts_for_path(
-                    PathKey::namespaced(COMMIT_METADATA_NAMESPACE, file.title.as_str().into()),
+                    PathKey::namespaced(COMMIT_METADATA_NAMESPACE, file.title.as_unix_str().into()),
                     buffer.clone(),
                     vec![Point::zero()..buffer.read(cx).max_point()],
                     0,
@@ -193,7 +193,7 @@ impl CommitView {
                             .collect::<Vec<_>>();
                         let path = snapshot.file().unwrap().path().clone();
                         let _is_newly_added = multibuffer.set_excerpts_for_path(
-                            PathKey::namespaced(FILE_NAMESPACE, path.as_str().into()),
+                            PathKey::namespaced(FILE_NAMESPACE, path.as_unix_str().into()),
                             buffer,
                             diff_hunk_ranges,
                             multibuffer_context_lines(cx),
@@ -275,7 +275,7 @@ impl language::File for CommitMetadataFile {
     }
 
     fn full_path(&self, _: &App) -> PathBuf {
-        PathBuf::from(self.title.as_str().to_owned())
+        PathBuf::from(self.title.as_unix_str().to_owned())
     }
 
     fn file_name<'a>(&'a self, _: &'a App) -> &'a str {