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, 3 insertions, 3 deletions

diff --git a/tests/misc/comm b/tests/misc/comm
index c727f80fc..905b5f862 100755
--- a/tests/misc/comm
+++ b/tests/misc/comm
@@ -57,7 +57,7 @@ my @Tests =
 
    # invalid missing command line argument (1)
    ['missing-arg1', $inputs[0], {EXIT=>1},
-    {ERR => "$prog: missing operand after `a'\n"
+    {ERR => "$prog: missing operand after 'a'\n"
         . "Try '$prog --help' for more information.\n"}],
 
    # invalid missing command line argument (both)
@@ -67,7 +67,7 @@ my @Tests =
 
    # invalid extra command line argument
    ['extra-arg', @inputs, 'no-such', {EXIT=>1},
-    {ERR => "$prog: extra operand `no-such'\n"
+    {ERR => "$prog: extra operand 'no-such'\n"
         . "Try '$prog --help' for more information.\n"}],
 
    # out-of-order input
@@ -133,7 +133,7 @@ my @Tests =
 
    # invalid empty delimiter
    ['delim-empty', '--output-delimiter=', @inputs, {EXIT=>1},
-    {ERR => "$prog: empty `--output-delimiter' not allowed\n"}],
+    {ERR => "$prog: empty '--output-delimiter' not allowed\n"}],
 
    # invalid dual delimiter
    ['delim-dual', '--output-delimiter=,', '--output-delimiter=+',