For --file-size, one should be able to differentiate files and standard input #815

The --file-size option is useful to immediately get the size of the (possibly preprocessed) file. However, it is also honored with the standard input while one may not want it in this case, because the whole content is not necessarily available (contrary to a file):

{ echo ab ; sleep 3 ; echo cd; } | less --file-size

takes 3 seconds to get ab displayed

So, for use with the LESS environment variable, either --file-size should be ignored with the standard input or there should be a separate option.