This problem appeared with my most recent Cygwin update that included an 
update to "vim".

My Cygwin installation now show vim version 9.0.2115.

Launching VIM from the shell running in a mintty window using the full 
pathname "/usr/bin/vim" works fine.

But launching "/usr/bin/vi" (which has worked fine for many years, until 
the most recent update), results in a long string of startup E319 errors:

>     $ /usr/bin/vi
>     Error detected while processing /usr/share/vim/vim90/filetype.vim:
>     line   11:
>     E319: Sorry, the command is not available in this version: let
>     did_load_filetypes = 1
>     line   14:
>     E319: Sorry, the command is not available in this version: let
>     s:cpo_save = &cpo
>     line   48:
>     E319: Sorry, the command is not available in this version: func
>     s:StarSetf(ft)
>     line   52:
>     E319: Sorry, the command is not available in this version: endfunc
    etc. etc.

Note that the startup errors appear only when using the full pathname 
"/usr/bin/vi". Using the command name alone ("vi") relying on the search 
path does not trigger the startup errors; using either the full pathname 
"/usr/bin/vim" or the command name alone "vim" relying on the search 
path does not trigger the startup errors.

I encountered this because some of my longtime 'convenience' Windows 
desktop links were launching a mintty window using "vi":

>     Target: C:\cygwin64\bin\mintty.exe -i /Cygwin-Terminal.ico
>     /usr/bin/vi /<targetfile>/

Easily fixed for me by changing "vi" to "vim". But don't know whether 
this change in behavior has any other implications?

Beau