setup-cygwin.bat:

  support to run it without parameters
  check setup.exe exists or not before setup

windows/scripts/setup-cygwin.bat

 @ECHO OFF
 SETLOCAL
 
-SET CYGWINHOME=%~1
+SET CYGWINHOME=%~1\
 SET CYGWINROOT="%~1\cygwin"
-SET DOWNLOADPATH="%CYGWINHOME%\cygwin-packages"
-SET SETUPFILE="%CYGWINHOME%\setup.exe"
+
+IF NOT "%CYGWINHOME%" == "" GOTO INIT
+
+SET CYGWINHOME=%~dp0
+SET CYGWINROOT="%~dp0cygwin"
+
+:INIT
+SET DOWNLOADPATH="%CYGWINHOME%cygwin-packages"
+SET SETUPFILE="%CYGWINHOME%setup.exe"
 SET OPTIONS=--no-shortcuts --no-startmenu --quiet-mode --no-verify
 
+IF NOT EXIST %SETUPFILE% GOTO START
+ECHO Missing %SETUPFILE%
+ENDLOCAL
+EXIT 1
+
+START:
+
 IF NOT "%2" == "" GOTO REMOTE_INSTALL
 
 :LOCAL_INSTALL