Add a simple pre-commit git hook to verify formatting

Author: jessebraham

README.md

@@ -20,6 +20,16 @@ A library and command-line tool for flashing Espressif devices.
 
 For more information and installation instructions, please refer to the `espflash` package's [README](./espflash/README.md).
 
+## Git Hooks
+
+We provide a simple `pre-commit` hook to verify the formatting of each package prior to committing changes. This can be enabled by placing it in the `.git/hooks/` directory:
+
+```bash
+$ cp pre-commit .git/hooks/pre-commit
+```
+
+When using this hook, you can choose to ignore its failure on a per-commit basis by committing with the `--no-verify` flag; however, you will need to be sure that all packages are formatted when submitting a pull request.
+
 ## License
 
 Licensed under either of:

pre-commit

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+# Exit immediately on first non-zero status from a command in the script.
+set -o errexit
+
+# Ensure all tools being used are available.
+command -v "cargo" >/dev/null 2>&1 || { echo >&2 "The 'cargo' command is not installed, exiting"; exit 1; }
+command -v "rustfmt" >/dev/null 2>&1 || { echo >&2 "The 'rustfmt' command is not installed, exiting"; exit 1; }
+
+# Check the formatting of all Rust code in the workspace.
+cargo fmt --all -- --check