I've been using default shell in Emacs (not eshell) for some time, defined some useful macros etc. Installed cygwin and now my default shell is bash. All of my macros and functions stopped working. Bash is a good choice, but I really want to go back to a default shell so I don't have to redefine and rewrite all my functions, macros, and scripts. I know how to set a shell to be used by M-x shell, what I don't know where is a vanilla/default shell for Emacs 26.1 on Windows 10.
According to this FAQ in the Emacs manual, the default shell on Windows is the standard
cmd.exe. It seems like the path to that executable is usually