book/development: git etiquette

book/src/development.md

@@ -1,11 +1,33 @@
 Notes for developers
 ====================
 
+## Making life easy for others
+
+> **Write useful commit messages.**
+
+If your commit is changing a specific module in the code and not
+touching other parts of the codebase (as should be the case 99% of the
+time), consider writing a useful commit message that also mentions
+which module was changed.
+
+For example, a message like:
+
+> `added foo`
+
+is not as clear as
+
+> `crypto/keypair: Added foo method for Bar struct.`
+
+Also keep in mind that commit messages can be longer than a single
+line, so use it to your advantage to explain your commit and
+intentions.
+
+
 ## cargo fmt pre-commit hook
 
 To ensure every contributor uses the same code style, make sure
-you run `cargo fmt` before committing. You can force yourself to do
-this by creating a git `pre-commit` hook like the following:
+you run `cargo +nightly fmt` before committing. You can force yourself
+to do this by creating a git `pre-commit` hook like the following:
 
 ```shell
 #!/bin/sh