Validate command line arguments at startup

[tbarusseau]

When running git cm with a misspelled/completely wrong argument on the command line, it only fails at the very end:

$ git cm woops!
✔ Select the type of change that you're committing: · perf: A code change that improves performance
✔ Denote the scope of this change (compiler, runtime, stdlib, etc.): · 
✔ Write a short, imperative tense description of the change: · 
✔ Provide a longer description of the change: · 
✔ Are there any breaking changes? · no
✔ Does this change affect any open issues? · no
thread 'main' panicked at 'Failed to open git repository: Error { code: -3, klass: 2, message: "failed to resolve path \'woops!\': No such file or directory" }', /home/tbarusseau/.cargo/registry/src/github.com-1ecc6299db9ec823/git-cm-0.1.1/src/git.rs:79:16
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

It should fail at the very beginning.

[mainrs]

It does actually happen because you can specify the path to a repository as the first argument. Move one up and run it again: cd .. && git cm folder

[tbarusseau]

I mean the issue is that it only fails at the very end, after you've completely typed your commit 😄

[mainrs]

That's when it actually tries to open the repository :) And since the repo doesn't exist under the folder name woops! it fails with a panic.