Multiple config file names feature (#1101)

* Add multiple configuration file names feature

* Add '.rustfmt.toml' in README file

* Clean up configuration file code

* Make config file names constant

* Use only one blank line

README.md

@@ -124,9 +124,10 @@ notes above on running rustfmt.
 ## Configuring Rustfmt
 
 Rustfmt is designed to be very configurable. You can create a TOML file called
-rustfmt.toml, place it in the project directory and it will apply the options
-in that file. See `rustfmt --config-help` for the options which are available,
-or if you prefer to see source code, [src/config.rs](src/config.rs).
+`rustfmt.toml` or `.rustfmt.toml`, place it in the project or any other parent
+directory and it will apply the options in that file. See `rustfmt
+--config-help` for the options which are available, or if you prefer to see
+source code, [src/config.rs](src/config.rs).
 
 By default, Rustfmt uses a style which (mostly) conforms to the
 [Rust style guidelines](https://github.com/rust-lang/rust/tree/master/src/doc/style).
@@ -148,8 +149,9 @@ options covering different styles. File an issue, or even better, submit a PR.
     #[rustfmt_skip]  // requires nightly and #![feature(custom_attribute)] in crate root
     #[cfg_attr(rustfmt, rustfmt_skip)]  // works in stable
     ```
-* When you run rustfmt, place a file named rustfmt.toml in target file
-  directory or its parents to override the default settings of rustfmt.
+* When you run rustfmt, place a file named `rustfmt.toml` or `.rustfmt.toml` in
+  target file directory or its parents to override the default settings of
+  rustfmt.
 * After successful compilation, a `rustfmt` executable can be found in the
   target directory.
 * If you're having issues compiling Rustfmt (or compile errors when trying to

src/bin/rustfmt.rs

@@ -109,20 +109,24 @@ fn lookup_project_file(dir: &Path) -> FmtResult<Option<PathBuf>> {
 
     current = try!(fs::canonicalize(current));
 
+    const CONFIG_FILE_NAMES: [&'static str; 2] = [".rustfmt.toml", "rustfmt.toml"];
+
     loop {
-        let config_file = current.join("rustfmt.toml");
-        match fs::metadata(&config_file) {
-            // Only return if it's a file to handle the unlikely situation of a directory named
-            // `rustfmt.toml`.
-            Ok(ref md) if md.is_file() => return Ok(Some(config_file)),
-            // Return the error if it's something other than `NotFound`; otherwise we didn't find
-            // the project file yet, and continue searching.
-            Err(e) => {
-                if e.kind() != ErrorKind::NotFound {
-                    return Err(FmtError::from(e));
+        for config_file_name in &CONFIG_FILE_NAMES {
+            let config_file = current.join(config_file_name);
+            match fs::metadata(&config_file) {
+                // Only return if it's a file to handle the unlikely situation of a directory named
+                // `rustfmt.toml`.
+                Ok(ref md) if md.is_file() => return Ok(Some(config_file)),
+                // Return the error if it's something other than `NotFound`; otherwise we didn't
+                // find the project file yet, and continue searching.
+                Err(e) => {
+                    if e.kind() != ErrorKind::NotFound {
+                        return Err(FmtError::from(e));
+                    }
                 }
+                _ => {}
             }
-            _ => {}
         }
 
         // If the current directory has no parent, we're done searching.