Timeout interpreter {{{ ... }}} blocks after 15 seconds

Summary: Fixes T4149. This could be a little cleaner (configurable time limits, explicit timeout errors) but stop the major case of looping/infinite commands.

Test Plan: Added `sleep 5 &&` and set timeout to 1, saw an error + kill.

Reviewers: btrahan, skyronic

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4149

Differential Revision: https://secure.phabricator.com/D7651

src/infrastructure/markup/interpreter/PhabricatorRemarkupBlockInterpreterCowsay.php

@@ -29,6 +29,7 @@ final class PhabricatorRemarkupBlockInterpreterCowsay
       $tongue,
       $cow);
 
+    $future->setTimeout(15);
     $future->write($content);
 
     list($err, $stdout, $stderr) = $future->resolve();

src/infrastructure/markup/interpreter/PhabricatorRemarkupBlockInterpreterFiglet.php

@@ -14,6 +14,7 @@ final class PhabricatorRemarkupBlockInterpreterFiglet
     }
 
     $future = id(new ExecFuture('figlet'))
+      ->setTimeout(15)
       ->write(trim($content, "\n"));
 
     list($err, $stdout, $stderr) = $future->resolve();

src/infrastructure/markup/interpreter/PhabricatorRemarkupBlockInterpreterGraphviz.php

@@ -14,6 +14,7 @@ final class PhabricatorRemarkupBlockInterpreterGraphviz
     }
 
     $future = id(new ExecFuture('dot -T%s', 'png'))
+      ->setTimeout(15)
       ->write(trim($content));
 
     list($err, $stdout, $stderr) = $future->resolve();
@@ -21,7 +22,9 @@ final class PhabricatorRemarkupBlockInterpreterGraphviz
     if ($err) {
       return $this->markupError(
         pht(
-          'Execution of `dot` failed, check your syntax: %s', $stderr));
+          'Execution of `dot` failed (#%d), check your syntax: %s',
+          $err,
+          $stderr));
     }
 
     $file = PhabricatorFile::buildFromFileDataOrHash(