tests: more automated quote adjustment

Relax initial regexp to match more instances, but add a
filter to avoid some invalid conversions.  Run this:

git grep -l "\`[^']*'" tests | xargs perl -pi -e '$q=q"'\''";' \
  -e '$q="$q\\$q$q"; /(= ?\`|\`expr|\`echo|\Q$q\E)/ and next;' \
  -e ' s/\`([^'\''"]*?'\'')/'\''$1/g'
The last disjunct in the above (...) filter is to exempt
any line that contains this string: '\''
With quoting like that, converting a ` to ' is likely to cause trouble,
so we'll handle those manually.  Here are three examples where
the exemption is required:

  *': `link-to-dir/'\'': hard link not allowed for directory'*) ;;
  printf 'creating file `%s'\''\n' $f
  'mv: inter-device move failed: `%s'\'' to `%s'\'';'\

1 files changed, 1 insertions, 1 deletions

diff --git a/tests/misc/od b/tests/misc/od
index 75ff2f159..46d4601d6 100755
--- a/tests/misc/od
+++ b/tests/misc/od
@@ -32,7 +32,7 @@ my $proc_file = '/proc/version';
 # Count the bytes in $proc_file, _by reading_.
 my $len = 0;
 open FH, '<', $proc_file
-  or die "$program_name: can't open `$proc_file' for reading: $!\n";
+  or die "$program_name: can't open '$proc_file' for reading: $!\n";
 while (defined (my $line = <FH>))
   {
     $len += length $line;