Avoid Wrapping Script Code In Quotes

[hostilefork]

The exec() command only runs a program with literal argument strings.
It does not know how to do things like expanding environment variables,
or piping/redirection. Hence the way to get "shell intelligence"
is to use exec() to run the sh process with the command line string
as a parameter.

But the method being used to do this was:

exec.exec(`sh -c \\"${script}"`)

This has problems, because wrapping the script in quotes creates
issues when the script itself contains quotes. Escaping the string
correctly is a non-trivial problem, which also would create "noise"
in the debug output which would add confusion.

http://mywiki.wooledge.org/BashFAQ/050

The easiest way to work around this here is to use the array form of
exec() to pass exactly two parameters to sh. No manipulation of the
script string is needed with this approach:

exec.exec("sh", ["-c", script])

There are more cases in the project of sh -c usage which should also
be changed, and likely abstracted (shellExec()?) But this small patch
just fixes the most important case for the user-provided script.

---

Additionally, this removes the escaped backslash (\\) from the
start of the executed command. That was presumably to suppress the
use of aliases:

https://unix.stackexchange.com/questions/524254/why-are-backslashes-included-in-this-shell-script

But because this is invoking a non-interactive shell session, aliases
would not apply. Hence the extra backslash shouldn't be needed.

[ychescale9]

Thanks!

[hostilefork]

@ychescale9 I notice that GitHub implements the custom shell: option by just writing the fragment of Yaml out to a temporary file and then running that.

This could offer benefits of wrapping long lines with backslash, handling #comments, etc.

Is there a reason not to do this here? You get the feature of erroring out on any line with -e, so that the script will stop if any step fails. The settings GitHub uses are:

bash --noprofile --norc -eo pipefail {0}

Where {0} is substituted with the temporary file created.

Offering the option of specifying a shell: would be ideal, but the default having -e is important.

[ychescale9]

@hostilefork Thanks for the input. I haven't looked into better backslash support, but if you can come up with something without breaking change feel free to send a PR:)

Thanks again for the contributions!