Describe the bug

Attempted to use a custom shell on Windows. Using MSYS2, and wanted to use its bash/sh, rather than Git's. Path has been set to do so.

In https://github.com/actions/runner/blob/master/docs/adrs/0277-run-action-shell-options.md, it states:

'The first word of the formatted string is assumed to be a command, and we attempt to locate its full path'

It seems this is done without taking into account what Path has been defined in the workflow file.

I tried both bash and sh, the sh text was sh.exe -e {0}, and it always ran the shell from
C:\Program Files\Git\bin even though the Path had the correct MSYS2 folder before the Git folder(s).

EDIT: Changing the path searched would be a breaking change. So, if possible, allowing the first full 'word' to be a full path to the command and checking for its existence before searching Path would probably be better...