Answer by Mike for How to add more commands to Git Bash?

If using Git bash for Windows (MinGW64), I had a very hard time getting rsync to be added to it. kept getting error: dup() in/out/err failed

Instead, using Cygwin worked eventually.

Steps I took to use rysnc in Gitbash for Windows

1. Install gitbash for windows
2. Install cygwin64
3. Add the cygwin path to the Windows path variable

   Windows-> System->advanced Setings->Environment Variables

   Add a path for C:\cygwin64\bin\

4. Close and re-open gitbashNow gitbash will find the rsync.exe in the cygwin\bin
5. I was getting an incompatible version error for cygwin1.dll

   *** fatal error - cygheap base mismatch detected

6. Although some said a reboot will fix this, it did not.
7. To resolve the version error, I copied the cygwin\bin directory from an older version of cygwin - version 1.7.30 worked