This file describes the more significant of the changes
made by Silicon Graphics, during its port of DIFF 1.15.
The file "Changes.gnu-sgi.diff.out" contains a diff
(using -uw options) output between the original source
and the final SGI port, for each *.c and *.h file.

As part of the port, SGI:

1) optimized performance in the case that the files
   being diff'd don't fit comfortably in main memory.
   In this large file case, if no GNU specific options
   are specified, and if /usr/bin/odiff is present,
   then odiff is automatically invoked, since it is
   much faster on huge files.  This port of GNU diff
   is typically faster on files that fit in main memory,
   thanks in part to its use of mmap, and to a quite
   different algorithm optimized for this case.

2) optimized performance in the case that the two
   files being diff'd are identical.  Consequently
   diff of two identical files is actually quite
   a bit faster than "cmp" of the same two files.

3) Dropped support for GNU's +longoptions, in part
   since they are changing the syntax to --longoption
   in future GNU diff releases, and it didn't make
   sense to support the +longoption form for just
   this single release from SGI.

4) added the local SGI "diff -x" option, for excluding
   subtrees on a recursive diff.

5) determine if files are binary (which by default
   can result in the message: Binary files %s and %s differ)
   by checking for NUL bytes in the first BUFSIZ (8k)
   bytes.  This NUL check is consistent with SVR4
   and with previous versions of diff on SGI systems.
   The GNU source for diff 1.15 checked instead
   for characters that were not in the ISO 8859 set.

				Silicon Graphics
				Dec 29, 1992