Improve the guidance on Cargo.lock in Rust.gitignore

See the following for more information:
 - https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
 - https://doc.rust-lang.org/cargo/faq.html#why-do-binaries-have-cargolock-in-version-control-but-not-libraries

Rust.gitignore

@@ -3,8 +3,10 @@
 debug/
 target/
 
-# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
-# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
+# If this is a library or crate (that other Rust projects will depend upon), keep Cargo.lock in your .gitignore.
+# If you’re building a binary or system library with crate-type of staticlib or cdylib, remove Cargo.lock from your .gitignore.
+# If you're curious about why that is, see "Why do binaries have Cargo.lock in version control, but not libraries?" in the FAQ.
+# https://doc.rust-lang.org/cargo/faq.html#why-do-binaries-have-cargolock-in-version-control-but-not-libraries
 Cargo.lock
 
 # These are backup files generated by rustfmt