What is this?

I decided to approach learning Rust through recreating common CLI tools. rat is a simple program that prints out files. rat supports the standard cat flags:

-A, --show-all           equivalent to -vET
-b, --number-nonblank    number nonempty output lines, overrides -n
-e                       equivalent to -vE
-E, --show-ends          display $ at end of each line
-n, --number             number all output lines
-s, --squeeze-blank      suppress repeated empty output lines
-t                       equivalent to -vT
-T, --show-tabs          display TAB characters as ^I
-v, --show-nonprinting   use ^ and M- notation, except for LFD and TAB
    --help        display this help and exit
    --version     output version information and exit

Things to redo/fix

• Make reading files/stdin buffered
• Make SqueezeBlanks replace chunks of newlines at once instead of one by one.
• Maybe ignore this, unnecessary dedup: Make flags apply all at once instead of constantly looping thru rmatch_indices.
• Make testing suite with random inputs that diff's cat and rat - maybe bash script.