I wonder what lessons were learned that could benefit others who want to port command line tools from C to Rust, e.g. particular idioms or re-usable functions (error handling, logging, defaults/dot-file management, command line option parsing).

There was a book called "Dr. Dobb's C-tools", which had the commented source code of a C compiler, assembler, linker and std library, and it greatly benefitted me to go beyond K&R's book towards understand the idioms of C programing.