Handle failed exit codes elegantly

[EverlastingBugstopper]

Instead of printing out this error:

$ wrangler generate my-rust https://github.com/EverlastingBugstopper/rustwasm-worker-template/🌀  🐑  Generating a new rust worker project with name 'my-rust'...
🔧   Creating project called `my-rust`...
Error: ⛔   Target directory already exists, aborting!
Error: failed to execute `"/Users/averyharnish/.cargo/bin/cargo-generate" "generate" "--git" "https://github.com/EverlastingBugstopper/rustwasm-worker-template/" "--name" "my-rust" "--force"`: exited with exit code: 1

print out this error that lets people copy and paste the command we tried to run easier (before it had a bunch of quotes in it):

$ wrangler generate my-rust https://github.com/EverlastingBugstopper/rustwasm-worker-template/
🌀  🐑  Generating a new worker project with name 'my-rust'...
🔧   Creating project called `my-rust`...
Error: ⛔   Target directory already exists, aborting!
Error: command exited with exit code: 1
`/Users/averyharnish/.cargo/bin/cargo-generate generate --git https://github.com/EverlastingBugstopper/rustwasm-worker-template/ --name my-rust --force`

[EverlastingBugstopper]

reason i'm looking at this is because of cargo-generate/cargo-generate#198

[exvuma]

While we are at it, could we remove these redundant lines?

🌀  🐑  Generating a new worker project with name 'my-rust'...
🔧   Creating project called `my-rust`...

seems those lines are saying the same thing?

[EverlastingBugstopper]

Totally!

[gabbifish]

same comment as other PR... I liked the ordering of printouts in the old message more, actually! Feel free to keep the replace logic though.

[xtuc]

Why does the command_name have quotes? Do we need to add them?

[EverlastingBugstopper]

I'm not entirely sure why it has quotes, I think it has something to do with the implementation of Display on Command (although I'm not sure). After this the quotes are removed though - I don't think we are the ones that implemented the quotes in the first place.