Merge pull request rust-lang#22010 from erfanio/rustfmt-fix

Fix rustfmt relative custom command

Author: Veykril

src/tools/rust-analyzer/crates/rust-analyzer/src/handlers/request.rs

@@ -2442,8 +2442,7 @@ fn run_rustfmt(
         }
         RustfmtConfig::CustomCommand { command, args } => {
             let cmd = Utf8PathBuf::from(&command);
-            let target_spec =
-                crates.first().and_then(|&crate_id| snap.target_spec_for_file(file_id, crate_id));
+            let target_spec = TargetSpec::for_file(snap, file_id).ok().flatten();
             let extra_env = snap.config.extra_env(source_root_id);
             let mut cmd = match target_spec {
                 Some(TargetSpec::Cargo(_)) => {