Fix linters

Summary:
Two fixes:
1. if cpplint is not present on the system, don't return a confusing error in the linter
2. Add include_alpha, which means our includes should be sorted lexicographically

Test Plan: Tried unsorting our includes, lint complained

Reviewers: rven, ljin, yhchiang, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D28845

db/column_family.cc

@@ -19,12 +19,12 @@
 #include <algorithm>
 #include <limits>
 
+#include "db/compaction_picker.h"
 #include "db/db_impl.h"
-#include "db/job_context.h"
-#include "db/version_set.h"
 #include "db/internal_stats.h"
-#include "db/compaction_picker.h"
+#include "db/job_context.h"
 #include "db/table_properties_collector.h"
+#include "db/version_set.h"
 #include "db/write_controller.h"
 #include "util/autovector.h"
 #include "util/hash_skiplist_rep.h"

linters/cpp_linter/FbcodeCppLinter.php

@@ -31,7 +31,7 @@ class FbcodeCppLinter extends ArcanistLinter {
                              $this->getEngine()->getFilePathOnDisk($p));
         } else {
           $futures[$p] = new ExecFuture("%s %s 2>&1",
-            self::CPPLINT, $this->getEngine()->getFilePathOnDisk($p));
+            $CPP_LINT, $this->getEngine()->getFilePathOnDisk($p));
         }
       }
 
@@ -68,6 +68,9 @@ class FbcodeCppLinter extends ArcanistLinter {
   }
 
   private function getCppLintOutput($path) {
+    if (!array_key_exists($path, $this->rawLintOutput)) {
+      return array();
+    }
     list($output) = $this->rawLintOutput[$path];
 
     $msgs = array();

linters/cpp_linter/cpplint.py

@@ -213,7 +213,7 @@ _ERROR_CATEGORIES = [
 # flag. By default all errors are on, so only add here categories that should be
 # off by default (i.e., categories that must be enabled by the --filter= flags).
 # All entries here should start with a '-' or '+', as in the --filter= flag.
-_DEFAULT_FILTERS = ['-build/include_alpha']
+_DEFAULT_FILTERS = []
 
 # We used to check for high-bit characters, but after much discussion we
 # decided those were OK, as long as they were in UTF-8 and didn't represent