saveAs [name] [encoding]
name
would be copied to the file name box in the save dialog.
saveAs [name] [encoding]
name
would be copied to the file name box in the save dialog.
One more suggestion.
It would be better, if it can take file filter as argument. (i.e. file type *.type] is by default selected)
cmd = sublime.Window()
cmd.runCommand("saveAs","*.txt")