Download the package: http://www2.futureware.at/~nickoe/msys2-mirror/msys/x86_64/rsync-3.1.2-2-x86_64.pkg.tar.xz
Extract it and move rsync.exe
to %HOMEDRIVE%%HOMEPATH%\AppData\Local\Programs\Git\usr\bin
.
open windows cmd prompt.. maybe an admin one..
cd %TEMP%
curl http://www2.futureware.at/~nickoe/msys2-mirror/msys/x86_64/rsync-3.1.2-2-x86_64.pkg.tar.xz -o rsync.txz
tar -xvf rsync.txz
cp usr/bin/rsync.exe "%ProgramFiles%\Git\usr\bin"
It doesn't.
But I have been thinking of trying to use cygrunsrv installed by pacman.
The instructions are incomplete here...
https://github.com/dgleba/gitportable-pacman/blob/master/README__portable.git4windows.msys2.add.pacman..2021-08-07rsync.cygrunsrv.know.txt
I have used cygrunsrv in cygwin. I haven't tried it in msys2 yet. Below is how I have done it in cygwin. Maybe it will work in msys2.