fix(fmt): return diff if source from stdin

Author: grandizzy

crates/forge/src/cmd/fmt.rs

@@ -127,12 +127,15 @@ impl FmtArgs {
                     let path = source_unit.file.name.as_real();
                     let original = source_unit.file.src.as_str();
                     let formatted = forge_fmt::format_ast(gcx, source_unit, fmt_config.clone())?;
+                    let from_stdin = path.is_none();
 
-                    if original == formatted {
+                    // If no diff then continue only if source loaded from stdin.
+                    // <https://github.com/foundry-rs/foundry/issues/11871>
+                    if original == formatted && (!from_stdin || self.check || self.raw) {
                         return None;
                     }
 
-                    if self.check || path.is_none() {
+                    if self.check || from_stdin {
                         let summary = if self.raw {
                             formatted
                         } else {