When you compare an empty file, such as /dev/null, with a non-empty file,
Solaris cmp complains on stderr with "cmp: EOF on /dev/null", even if the
-s argument is present. GNU cmp makes the complaint, but silences it with
-s. We can change the pdiff utility to simply redirect stderr to /dev/null
so that we don't have to worry about this difference in the test files.
Before this patch, some tests using external "diff" command via
extdiff extension fail on Solaris, because of incompatibility of
"diff" command and its output.
For example, system standard "diff" (= /usr/bin/diff) on Solaris
differs from GNU diff in points below:
- "-N" (treat absent files as empty) option isn't supported
- files are examined not in dictionary order
(maybe, in order in storage)
This patch introduces portable diff script "pdiff" and make tests use
it via extdiff extension.
For portability of tests, this patch invokes "pdiff" script with
explicit "sh", because standard shell of runtime platform ("cmd.exe"
on Windows) is used at first to invoke external diff command.
