- Instead of changing the current directory with `env::set_current_dir`
to be implicitly inherited by subprocesses, we now use
`Command::current_dir` to set it explicitly. This feels much better,
since we aren't dependent on the implicit state of the process's
current directory.
- Subcommand execution is much improved.
- Added a ton of tests for config parsing, config execution, working
dir, and search dir.
- Error messages are improved. Many more will be colored.
- The Config is now onwed, instead of borrowing from the arguments and
the `clap::ArgMatches` object. This is a huge ergonomic improvement,
especially in tests, and I don't think anyone will notice.
- `--edit` now uses `$VISUAL`, `$EDITOR`, or `vim`, in that order,
matching git, which I think is what most people will expect.
- Added a cute `tmptree!{}` macro, for creating temporary directories
populated with directories and files for tests.
- Admitted that grammer is LL(k) and I don't know what `k` is.
Moves the code which executes subcommands into Subcommand:run,
delegating to separate functions for each subcommand. This reduces the
disgustingness of `run::run` a bit, and paves the way for future
refactoring and cleanup.
- Differentiate between `arg`s, which are flags and options, and `cmd`s,
which are mutually exclusive subcommands
- Replace string literals, like "EVALUATE", with constants, like
`cmd::EVALUATE`, since they're slightly less error prone.
- Remove `Config::evaluate`, and handle it like other subcommands
