When outputting lines in normal or context format, or outputting an
unchanged line in unified format, diff normally outputs a
blank just before each line. If the line is empty, the output of
diff therefore contains trailing blanks even though the
input does not contain them. For example, when outputting an
unchanged empty line in context format, diff normally
outputs a line with two leading spaces.
Some text editors and email agents routinely delete trailing blanks,
so it can be a problem to deal with diff output files that contain
them. You can avoid this problem with the
--suppress-blank-empty option. It causes diff to
omit trailing blanks at the end of output lines in normal, context,
and unified format, unless the trailing blanks were already present in
the input. This changes the output format slightly, so that output
lines are guaranteed to never end in a blank unless an input line ends
in a blank. This format is less likely to be munged by text editors
or by transmission via email. It is accepted by GNU
patch as well.