Portable Cygwin: Windows Registry Entries?

[Matthew Sheets]

>> Are there any flags, options, special environment variables, etc. 
>> that would prevent Cygwin from making any registry changes?

> You can prevent this with the '--no-write-registry' setup option.

Thank you!  Is this option currently considered stable / safe for
general use?  It doesn't appear to be listed among Setup's
documented command-line arguments:
* https://cygwin.com/faq.html#faq.setup.cli


At least with the option combinations I've tested, it appears that
Setup can be made to avoid writing to the registry.

Additionally, the "--root" option seems to work as a means
to facilitate Setup handling the changing path of a portable
installation.  (This also works for keeping Setup outside the
installation root.)

On the Cygwin usage side of things, registry entries do appear
following execution of commands from a DOS prompt such as
"bash --login" (like found in Cygwin.bat) and "cygcheck -s".


Thank you,
Matthew