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/cat-proc b/tests/misc/cat-proc
index 99e064bf9..082c727e0 100755
--- a/tests/misc/cat-proc
+++ b/tests/misc/cat-proc
@@ -1,5 +1,5 @@
 #!/bin/sh
-# Ensure that cat -E produces same output as cat, module `$'s,
+# Ensure that cat -E produces same output as cat, module '$'s,
 # even when applied to a file in /proc.
 
 # Copyright (C) 2006-2012 Free Software Foundation, Inc.