refactor: CheckFreshness and DiffDiagram take &str instead of &Path

crates/presentation/src/lib.rs

@@ -46,10 +46,12 @@ pub fn run(args: Cli) -> Result<()> {
         let existing_path = args.output.as_ref().ok_or_else(|| {
             anyhow::anyhow!("--check requires --output to specify the file to check against")
         })?;
+        let existing_content = std::fs::read_to_string(existing_path)
+            .map_err(|e| anyhow::anyhow!("cannot read {existing_path}: {e}"))?;
         let up_to_date = CheckFreshness {
             graph: &graph,
             renderer: &*renderer,
-            existing_path: std::path::Path::new(existing_path),
+            existing_content: &existing_content,
         }
         .execute()?;
         if up_to_date {
@@ -222,10 +224,12 @@ fn run_diff(args: &Cli, existing_path: &std::path::Path) -> Result<()> {
     let graph = build_graph(args, level)?;
     let renderer = create_renderer(&args.format, level, !args.no_weights)?;
 
+    let existing_content = std::fs::read_to_string(existing_path)
+        .map_err(|e| anyhow::anyhow!("cannot read {}: {e}", existing_path.display()))?;
     let diff = DiffDiagram {
         graph: &graph,
         renderer: &*renderer,
-        existing_path,
+        existing_content: &existing_content,
     }
     .execute()?;