Accept a String Argument to --shell

[Kurt-von-Laven]

Description

Execute commands in the shell lint-staged is run in when the --shell option is passed. Lint-staged uses execa, which also accepts a --shell option: "If true, runs file inside of a shell. Uses /bin/sh on UNIX and cmd.exe on Windows. A different shell can be specified as a string." ~ https://github.com/sindresorhus/execa#shell

Since lint-staged ferries the --shell option through to execa, it would be ideal for it to also accept a string specifying a custom shell. This would allow lint-staged configs requiring the --shell option to function consistently on Unix and Windows development environments. N.B. Windows ships with Bash these days. An alternative solution would be to run lint-staged commands in the shell from which lint-staged was executed when --shell is passed. That would be more intuitive from the perspective of the developer committing code but perhaps less intuitive from the perspective of the developer authoring the lint-staged config.

Steps to reproduce

0. Run lint-staged (e.g., by committing in a repository with lint-staged configured) from Bash on Windows.
1. The lint-staged commands are run in Command Prompt.

Environment

• OS: Windows 10
• Node.js: v16.14.0
• lint-staged: v11.0.0

[okonet]

This sounds like a great candidate for a PR!

[iiroj]

Seems straightforward enough, I will try to make a quick PR.