Guarantee repositories have unique local paths

Summary:
Ref T4039. Long ago these were more freely editable and there were some security concerns around creating a repository, then setting its local path to point somewhere it shouldn't.

Local paths are no longer editable so there's no real reason we need to provide a uniqueness guarantee anymore, but you could still make a mistake with `bin/repository move-paths` by accident, and it's a little cleaner to pull them out into their own column with a key.

(We still don't -- and, largely can't -- guarantee that two paths aren't //equivalent// since one might be symlinked to the other, or symlinked only on some hosts, or whatever, but the primary value here is as a sanity check that you aren't goofing things up and pointing a bunch of repositories at the same working copy by mistake.)

Test Plan:
  - Ran migrations.
  - Grepped for `local-path`.
  - Listed and moved paths with `bin/repository`.
  - Created a new repository, verified its local path populated correctly.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T4039

Differential Revision: https://secure.phabricator.com/D15837

resources/sql/autopatches/20160503.repo.01.lpath.sql

@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_repository.repository
+  ADD localPath VARCHAR(128) COLLATE {$COLLATE_TEXT};

resources/sql/autopatches/20160503.repo.02.lpathkey.sql

@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_repository.repository
+  ADD UNIQUE KEY `key_local` (localPath);

resources/sql/autopatches/20160503.repo.03.lpathmigrate.php

@@ -0,0 +1,57 @@
+<?php
+
+$table = new PhabricatorRepository();
+$conn_w = $table->establishConnection('w');
+
+$default_path = PhabricatorEnv::getEnvConfig('repository.default-local-path');
+$default_path = rtrim($default_path, '/');
+
+foreach (new LiskMigrationIterator($table) as $repository) {
+  $local_path = $repository->getLocalPath();
+  if (strlen($local_path)) {
+    // Repository already has a modern, unique local path.
+    continue;
+  }
+
+  $local_path = $repository->getDetail('local-path');
+  if (!strlen($local_path)) {
+    // Repository does not have a local path using the older format.
+    continue;
+  }
+
+  $random = Filesystem::readRandomCharacters(8);
+
+  // Try the configured path first, then a default path, then a path with some
+  // random noise.
+  $paths = array(
+    $local_path,
+    $default_path.'/'.$repository->getID().'/',
+    $default_path.'/'.$repository->getID().'-'.$random.'/',
+  );
+
+  foreach ($paths as $path) {
+    // Set, then get the path to normalize it.
+    $repository->setLocalPath($path);
+    $path = $repository->getLocalPath();
+
+    try {
+      queryfx(
+        $conn_w,
+        'UPDATE %T SET localPath = %s WHERE id = %d',
+        $table->getTableName(),
+        $path,
+        $repository->getID());
+
+      echo tsprintf(
+        "%s\n",
+        pht(
+          'Assigned repository "%s" to local path "%s".',
+          $repository->getDisplayName(),
+          $path));
+
+      break;
+    } catch (AphrontDuplicateKeyQueryException $ex) {
+      // Ignore, try the next one.
+    }
+  }
+}