Allow for /D to change install directory on the command line.

Modules/NSIS.template.in

@@ -18,7 +18,7 @@
   Var ADD_TO_PATH_ALL_USERS
   Var ADD_TO_PATH_CURRENT_USER
   Var INSTALL_DESKTOP
-
+  Var IS_DEFAULT_INSTALLDIR
 ;--------------------------------
 ;Include Modern UI
 
@@ -892,8 +892,19 @@ Function .onInit
   ; Reads components status for registry
   !insertmacro SectionList "InitSection"
 
+  ; check to see if /D has been used to change 
+  ; the install directory by comparing it to the 
+  ; install directory that is expected to be the
+  ; default
+  StrCpy $IS_DEFAULT_INSTALLDIR 0
+  StrCmp "$INSTDIR" "$PROGRAMFILES\@CPACK_PACKAGE_INSTALL_DIRECTORY@" 0 +2
+    StrCpy $IS_DEFAULT_INSTALLDIR 1
+  
   StrCpy $SV_ALLUSERS "JustMe"
-  StrCpy $INSTDIR "$DOCUMENTS\@CPACK_PACKAGE_INSTALL_DIRECTORY@"
+  ; if default install dir then change the default
+  ; if it is installed for JustMe
+  StrCmp "$IS_DEFAULT_INSTALLDIR" "1" 0 +2
+    StrCpy $INSTDIR "$DOCUMENTS\@CPACK_PACKAGE_INSTALL_DIRECTORY@"
 
   ClearErrors
   UserInfo::GetName
@@ -917,8 +928,9 @@ Function .onInit
     ;Get installation folder from registry if available
 
   done:
-  StrCmp $SV_ALLUSERS "AllUsers" 0 +2
-    StrCpy $INSTDIR "$PROGRAMFILES\@CPACK_PACKAGE_INSTALL_DIRECTORY@"
+  StrCmp $SV_ALLUSERS "AllUsers" 0 +3
+    StrCmp "$IS_DEFAULT_INSTALLDIR" "1" 0 +2
+      StrCpy $INSTDIR "$PROGRAMFILES\@CPACK_PACKAGE_INSTALL_DIRECTORY@"
 
   StrCmp "@CPACK_NSIS_MODIFY_PATH@" "ON" 0 noOptionsPage
     !insertmacro MUI_INSTALLOPTIONS_EXTRACT "NSIS.InstallOptions.ini"