Update cheatsheets

rustfmt

@@ -0,0 +1,21 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# rustfmt
+
+> Format Rust source code.
+> More information: <https://github.com/rust-lang/rustfmt>.
+
+- Format a file, overwriting the original file in-place:
+
+`rustfmt {{path/to/source.rs}}`
+
+- Check a file for formatting and display any changes on the console:
+
+`rustfmt --check {{path/to/source.rs}}`
+
+- Backup any modified files before formatting (the original file is renamed with a `.bk` extension):
+
+`rustfmt --backup {{path/to/source.rs}}`