Warn about converting arguments to `&str` in `std::process::Command`'s methods

Categories: Performance, Correctness, warn-by-default

warn-by-default because the author may want to verify the UTF-8 validly
of the expression.

Auto-apply suggestion ability

None. It's hard to make correct suggestion.

What it does

Check for convert from lossless OsStr-compatible types (Like Path, PathBuf)
to &str when passing to arguments of std::process::Command methods:

• Command::new
• Command::arg
• Command::args
• Command::env
• Command::envs
• Command::env_remove
• Command::current_dir

Known problems

The author may intend to verify the UTF-8 validly of the expression.

Example

use std::path::Path;
use std::process::Command;
// Assume this is the non UTF-8 path
let dest = Path::new("<non-utf8 path>");
Command::new("git")
    .args(&[
        "clone",
        "https://github.com/rust-lang/rust-clippy",
        &dest.to_string_lossy(),
    ])
    .status()
    .unwrap();

Could be written as:

use std::ffi::OsStr;
Command::new("git")
    .args(&[
        OsStr::new("clone"),
        OsStr::new("https://github.com/rust-lang/rust-clippy"),
        OsStr::new(dest),
    ])
    .status()
    .unwrap();

Start by examining the listed std::process::Command methods and the provided Rust example to determine how lossless OsStr-compatible values are converted to &str. Done means the lint detects these conversions, emits a warning without an auto-apply suggestion, and accounts for the stated UTF-8 validation concern.