Add Perl code check GitHub action

Add a run of `perltidy` to make sure that all the Perl code is
correctly formatted. Also fix the formatting of one file that did not
follow the style in `scripts/perltidyrc`.

.github/workflows/code_style.yaml

@@ -8,6 +8,18 @@ on:
       - prerelease_test
   pull_request:
 jobs:
+  perl_checks:
+    name: Check Perl code in tree
+    runs-on: ubuntu-20.04
+    steps:
+      - name: Install prerequisites
+        run: sudo apt install perltidy
+      - name: Checkout source
+        uses: actions/checkout@v2
+      - name: Format Perl files, if needed
+        run: find . -name '*.p[lm]' -exec perltidy --profile=scripts/perltidyrc {} +
+      - name: Check for diff
+        run: git diff --exit-code
   misc_checks:
     name: Check formatting, license and git hooks
     runs-on: ubuntu-20.04

test/perl/TimescaleNode.pm

@@ -32,7 +32,7 @@ sub get_new_ts_node
 {
 	my ($name, $class) = @_;
 
-    $class //= 'TimescaleNode';
+	$class //= 'TimescaleNode';
 
 	my $self = PostgresNode::get_new_node($name);
 	$self = bless $self, $class;
@@ -48,7 +48,8 @@ sub init
 	$self->SUPER::init(%kwargs);
 	# append into postgresql.conf from Timescale
 	# template config file
-	$self->append_conf('postgresql.conf', TestLib::slurp_file("$ENV{'BUILDIR'}/tsl/test/postgresql.conf"));
+	$self->append_conf('postgresql.conf',
+		TestLib::slurp_file("$ENV{'BUILDIR'}/tsl/test/postgresql.conf"));
 }
 
 # helper function to check output from PSQL for a query