tests: use "compare exp out", not "compare out exp"

Likewise, when an empty file is expected, use "compare /dev/null out",
not "compare out /dev/null". I.e., specify the expected/desired contents
via the first file name.  Prompted by a suggestion from Bruno Haible
in http://thread.gmane.org/gmane.comp.gnu.grep.bugs/4020/focus=29154

Run these commands:

    git grep -l -E 'compare [^ ]+ exp' \
      |xargs perl -pi -e 's/(compare) (\S+) (exp\S*)/$1 $3 $2/'
    git grep -l -E 'compare [^ ]+ /dev/null' \
      |xargs perl -pi -e 's/(compare) (\S+) (\/dev\/null)/$1 $3 $2/'

1 files changed, 4 insertions, 4 deletions

diff --git a/tests/pcre-z b/tests/pcre-z
index 169c44e8..99ebc43c 100755
--- a/tests/pcre-z
+++ b/tests/pcre-z
@@ -8,16 +8,16 @@ REGEX=a
 printf "%s\n0" abc def ghi aaa gah | tr 0 \\0 > in
 
 grep -z "$REGEX" in > exp 2>err || fail_ 'Cannot do BRE (grep -z) match.'
-compare err /dev/null || fail_ 'stderr not empty on grep -z.'
+compare /dev/null err || fail_ 'stderr not empty on grep -z.'
 
 # Sanity check the output
 test "$(grep -cz $REGEX in 2>err)" = 3 \
     || fail_ 'Incorrect BRE (grep -cz) match.'
-compare err /dev/null || fail_ 'stderr not empty on grep -cz.'
+compare /dev/null err || fail_ 'stderr not empty on grep -cz.'
 
 fail=0
 grep -Pz "$REGEX" in > out 2>err || fail=1
-compare out exp || fail=1
-compare err /dev/null || fail=1
+compare exp out || fail=1
+compare /dev/null err || fail=1
 
 Exit $fail