Auto-dereference list refs only if really refs.

This allows single-elements lists to not be guessed as a list reference
in list_has, which helps with bug 291357... but still doesn't explain
why old code that used list_has didn't have the same issue.

I have included a test case which fails and is likely related to the
reason though, so hopefully won't be hard to pin down from here.

CCBUG:291357

kdesrc-build

@@ -332,8 +332,13 @@ my $run_mode = 'build'; # Determines if updating, building, installing, etc.
     sub list_has(\@$)
     {
         my $value = pop;
+        my @list = @_;
+
         # Expand list references if present, otherwise use all params.
-        my @list = scalar @_ == 1 ? @{$_[0]} : @_;
+        if (scalar @_ == 1 && (ref $_[0] eq ref [])) {
+            @list = @{$_[0]};
+        }
+
         return scalar grep { "$_" eq "$value" } (@list);
     }
 

kdesrc-build-test.pl

@@ -211,6 +211,13 @@ $testModule->setupEnvironment();
 is($ctx->{env}->{'TESTY_MCTEST'}, 'yes', 'setting global set-env for modules');
 is($ctx->{env}->{'MOIN'}, '2', 'setting module set-env for modules');
 
+# Ensure that an empty {env} variable is not used.
+my $unlikelyEnvVar = 'KDESRC_BUILD_TEST_PATH';
+$ENV{$unlikelyEnvVar} = 'FAILED';
+$ctx->prependEnvironmentValue($unlikelyEnvVar, 'TEST_PATH');
+ok(defined $ctx->{env}->{$unlikelyEnvVar}, 'prependEnvironmentValue queues value');
+is($ctx->{env}->{$unlikelyEnvVar}, 'TEST_PATH:FAILED', 'prependEnvironmentValue queues in right order');
+
 # Ensure svn URL hierarchy is correct
 like(svn_module_url($testModule), qr{/home/kde/KDE/KDE/test$}, 'svn_module_url prefer module specific to global');
 $testModule->setOption('override-url', 'svn://annono');