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/tty-eof b/tests/misc/tty-eof
index eaaec35c8..d6c4a7714 100755
--- a/tests/misc/tty-eof
+++ b/tests/misc/tty-eof
@@ -67,7 +67,7 @@ $@
       my $exp = new Expect;
       $exp->log_user(0);
       $exp->spawn("$cmd 2> $stderr")
-        or (warn "$ME: cannot run `$cmd': $!\n"), $fail=1, next;
+        or (warn "$ME: cannot run '$cmd': $!\n"), $fail=1, next;
       # No input for cut -f2.
       $cmd =~ /^cut/
         or $exp->send("a b\n");