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, 2 insertions, 2 deletions

diff --git a/tests/rm/empty-name b/tests/rm/empty-name
index 192a60b4b..bb8307a50 100755
--- a/tests/rm/empty-name
+++ b/tests/rm/empty-name
@@ -44,10 +44,10 @@ my @Tests =
      # test-name options input expected-output
      #
      ['empty-name-1', "''", {EXIT => 1},
-      {ERR => "$prog: cannot remove `': No such file or directory\n"}],
+      {ERR => "$prog: cannot remove '': No such file or directory\n"}],
 
      ['empty-name-2', "a '' b", {EXIT => 1},
-      {ERR => "$prog: cannot remove `': No such file or directory\n"},
+      {ERR => "$prog: cannot remove '': No such file or directory\n"},
       {PRE => sub { mk_file qw(a b) }},
       {POST => sub {-f 'a' || -f 'b' and die "a or b remain\n" }},
      ],