When -v is passed with --list, display path to custom commands

[pwoolcoc]

With this change, output of cargo --list changes slightly when 1 or more -v flags are passed:

 ± ./target/debug/cargo --list -v
Installed Commands:
    add                  /path/to/home/.cargo/bin/cargo-add
    bench
    build
    canoe                /path/to/home/.cargo/bin/cargo-canoe
    check
    clean
    do                   /path/to/home/.cargo/bin/cargo-do
    doc
    fetch
    fmt                  /path/to/home/.cargo/bin/cargo-fmt
    ...

[rust-highfive]

r? @matklad

(rust_highfive has picked a reviewer for you, use r? to override)

[matklad]

Seems like a nifty idea to me!

@rust-lang/cargo thoughts about this new feature?

[alexcrichton]

Sounds neat to me!

[lukaslueg]

Maybe it makes sense to have a verbatim output of just the path-values, so the output may be easily consumed by another program via the shell? All that is required is for Installed commands: to be put to stderr instead of stdout; a single awk could extract the paths. If the output is just the paths (if they exist at all), it would be even easier.

[matklad]

@bors r+

Thanks @pwoolcoc

@lukaslueg do you have a particular use-case for this in mind though? I'd rather not make promises about particular output format until we have a solid understanding of the use-case.

[bors]

📌 Commit f76db9c has been approved by matklad

[bors]

⌛ Testing commit f76db9c with merge 00eb24d...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: matklad
Pushing 00eb24d to master...