When users browse to a submodule path in Diffusion explicitly, don't fatal

Summary: Ref T13030. See PHI254. This behavior could be cleaner than I've made it, but it fixes the "this is totally broken" issue, replacing a fatal/exception with an informative (just not terribly useful) page.

Test Plan:
  - Added a submodule to a repository.
  - In Diffusion, clicked some other file next to the submodule, then edited the URI to the submodule path instead.
    - Before patch: fatal.
    - After patch: relatively useful message about this being a submodule.

Note that it's normally hard to hit this URI directly. In the browse view, submodules are marked up as directories and linked to a separate submodule resolution flow.

{F5321524}

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13030

Differential Revision: https://secure.phabricator.com/D18831

src/applications/diffusion/conduit/DiffusionBrowseQueryConduitAPIMethod.php

@@ -52,6 +52,36 @@ final class DiffusionBrowseQueryConduitAPIMethod
           $commit,
           $path);
       } catch (CommandException $e) {
+        // The "cat-file" command may fail if the path legitimately does not
+        // exist, but it may also fail if the path is a submodule. This can
+        // produce either "Not a valid object name" or "could not get object
+        // info".
+
+        // To detect if we have a submodule, use `git ls-tree`. If the path
+        // is a submodule, we'll get a "160000" mode mask with type "commit".
+
+        list($sub_err, $sub_stdout) = $repository->execLocalCommand(
+          'ls-tree %s -- %s',
+          $commit,
+          $path);
+        if (!$sub_err) {
+          // If the path failed "cat-file" but "ls-tree" worked, we assume it
+          // must be a submodule. If it is, the output will look something
+          // like this:
+          //
+          //   160000 commit <hash> <path>
+          //
+          // We make sure it has the 160000 mode mask to confirm that it's
+          // definitely a submodule.
+          $mode = (int)$sub_stdout;
+          if ($mode & 160000) {
+            $submodule_reason = DiffusionBrowseResultSet::REASON_IS_SUBMODULE;
+            $result
+              ->setReasonForEmptyResultSet($submodule_reason);
+            return $result;
+          }
+        }
+
         $stderr = $e->getStderr();
         if (preg_match('/^fatal: Not a valid object name/', $stderr)) {
           // Grab two logs, since the first one is when the object was deleted.

src/applications/diffusion/data/DiffusionBrowseResultSet.php

@@ -3,6 +3,7 @@
 final class DiffusionBrowseResultSet extends Phobject {
 
   const REASON_IS_FILE              = 'is-file';
+  const REASON_IS_SUBMODULE         = 'is-submodule';
   const REASON_IS_DELETED           = 'is-deleted';
   const REASON_IS_NONEXISTENT       = 'nonexistent';
   const REASON_BAD_COMMIT           = 'bad-commit';

src/applications/diffusion/view/DiffusionEmptyResultView.php

@@ -40,6 +40,13 @@ final class DiffusionEmptyResultView extends DiffusionView {
         $body = pht('This path was an empty directory at %s.', $commit);
         $severity = PHUIInfoView::SEVERITY_NOTICE;
         break;
+      case DiffusionBrowseResultSet::REASON_IS_SUBMODULE:
+        $title = pht('Submodule');
+        // TODO: We could improve this, but it is normally difficult to
+        // reach this page for a submodule.
+        $body = pht('This path was a submodule at %s.', $commit);
+        $severity = PHUIInfoView::SEVERITY_NOTICE;
+        break;
       case DiffusionBrowseResultSet::REASON_IS_DELETED:
         $deleted = $this->browseResultSet->getDeletedAtCommit();
         $existed = $this->browseResultSet->getExistedAtCommit();