Merge pull request #2060 from tamird/doc-dump-default-config

Document `--dump-default-config` in README.md

README.md

@@ -208,7 +208,8 @@ options covering different styles. File an issue, or even better, submit a PR.
     ```
 * 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.
+  rustfmt. You can generate a file containing the default configuration with
+  `rustfm --dump-default-config rustfmt.toml` and customize as needed.
 * 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

@@ -128,8 +128,7 @@ fn make_opts() -> Options {
     opts.opt(
         "",
         "dump-default-config",
-        "Dumps the default configuration to a file and exits. PATH defaults to rustfmt.toml if \
-         omitted.",
+	"Dumps default configuration to PATH. PATH defaults to stdout, if omitted."
         "PATH",
         HasArg::Maybe,
         Occur::Optional,