diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
index b89c0d4c..c6e80dcb 100644
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -57,6 +57,8 @@ phutil_register_library_map(array(
     'ArcanistListWorkflow' => 'workflow/list',
     'ArcanistMarkCommittedWorkflow' => 'workflow/mark-committed',
     'ArcanistMercurialAPI' => 'repository/api/mercurial',
+    'ArcanistMercurialParser' => 'repository/parser/mercurial',
+    'ArcanistMercurialParserTestCase' => 'repository/parser/mercurial/__tests__',
     'ArcanistMergeWorkflow' => 'workflow/merge',
     'ArcanistNoEffectException' => 'exception/usage/noeffect',
     'ArcanistNoEngineException' => 'exception/usage/noengine',
@@ -123,6 +125,7 @@ phutil_register_library_map(array(
     'ArcanistListWorkflow' => 'ArcanistBaseWorkflow',
     'ArcanistMarkCommittedWorkflow' => 'ArcanistBaseWorkflow',
     'ArcanistMercurialAPI' => 'ArcanistRepositoryAPI',
+    'ArcanistMercurialParserTestCase' => 'ArcanistPhutilTestCase',
     'ArcanistMergeWorkflow' => 'ArcanistBaseWorkflow',
     'ArcanistNoEffectException' => 'ArcanistUsageException',
     'ArcanistNoEngineException' => 'ArcanistUsageException',
diff --git a/src/repository/api/mercurial/ArcanistMercurialAPI.php b/src/repository/api/mercurial/ArcanistMercurialAPI.php
index 8a02ae97..c288e37f 100644
--- a/src/repository/api/mercurial/ArcanistMercurialAPI.php
+++ b/src/repository/api/mercurial/ArcanistMercurialAPI.php
@@ -71,7 +71,7 @@ class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
       list($stdout) = execx(
         '(cd %s && hg outgoing --branch `hg branch` --limit 1 --style default)',
         $this->getPath());
-      $logs = $this->parseMercurialLog($stdout);
+      $logs = ArcanistMercurialParser::parseMercurialLog($stdout);
       if (!count($logs)) {
         throw new ArcanistUsageException("You have no outgoing changes!");
       }
@@ -88,7 +88,7 @@ class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
         '(cd %s && hg parents --style default --rev %s)',
         $this->getPath(),
         $oldest_rev);
-      $parents_logs = $this->parseMercurialLog($stdout);
+      $parents_logs = ArcanistMercurialParser::parseMercurialLog($stdout);
       $first_parent = head($parents_logs);
       if (!$first_parent) {
         throw new ArcanistUsageException(
@@ -106,7 +106,7 @@ class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
       $this->getPath(),
       $this->getRelativeCommit(),
       $this->getWorkingCopyRevision());
-    $logs = $this->parseMercurialLog($info);
+    $logs = ArcanistMercurialParser::parseMercurialLog($info);
 
     // Get rid of the first log, it's not actually part of the diff. "hg log"
     // is inclusive, while "hg diff" is exclusive.
@@ -182,7 +182,7 @@ class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
         '(cd %s && hg status)',
         $this->getPath());
 
-      $working_status = $this->parseMercurialStatus($stdout);
+      $working_status = ArcanistMercurialParser::parseMercurialStatus($stdout);
       foreach ($working_status as $path => $status) {
         $status |= self::FLAG_UNCOMMITTED;
         if (!empty($status_map[$path])) {
@@ -251,107 +251,6 @@ class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
     return $stdout;
   }
 
-  private function parseMercurialStatus($status) {
-    $result = array();
-
-    $status = trim($status);
-    if (!strlen($status)) {
-      return $result;
-    }
-
-    $lines = explode("\n", $status);
-    foreach ($lines as $line) {
-      $flags = 0;
-      list($code, $path) = explode(' ', $line, 2);
-      switch ($code) {
-        case 'A':
-          $flags |= self::FLAG_ADDED;
-          break;
-        case 'R':
-          $flags |= self::FLAG_REMOVED;
-          break;
-        case 'M':
-          $flags |= self::FLAG_MODIFIED;
-          break;
-        case 'C':
-          // This is "clean" and included only for completeness, these files
-          // have not been changed.
-          break;
-        case '!':
-          $flags |= self::FLAG_MISSING;
-          break;
-        case '?':
-          $flags |= self::FLAG_UNTRACKED;
-          break;
-        case 'I':
-          // This is "ignored" and included only for completeness.
-          break;
-        default:
-          throw new Exception("Unknown Mercurial status '{$code}'.");
-      }
-
-      $result[$path] = $flags;
-    }
-
-    return $result;
-  }
-
-  private function parseMercurialLog($log) {
-    $result = array();
-
-    $chunks = explode("\n\n", trim($log));
-    foreach ($chunks as $chunk) {
-      $commit = array();
-      $lines = explode("\n", $chunk);
-      foreach ($lines as $line) {
-        if (preg_match('/^(comparing with|searching for changes)/', $line)) {
-          // These are sent to stdout when you run "hg outgoing" although the
-          // format is otherwise identical to "hg log".
-          continue;
-        }
-        list($name, $value) = explode(':', $line, 2);
-        $value = trim($value);
-        switch ($name) {
-          case 'user':
-            $commit['user'] = $value;
-            break;
-          case 'date':
-            $commit['date'] = strtotime($value);
-            break;
-          case 'summary':
-            $commit['summary'] = $value;
-            break;
-          case 'changeset':
-            list($local, $rev) = explode(':', $value, 2);
-            $commit['local'] = $local;
-            $commit['rev'] = $rev;
-            break;
-          case 'parent':
-            if (empty($commit['parents'])) {
-              $commit['parents'] = array();
-            }
-            list($local, $rev) = explode(':', $value, 2);
-            $commit['parents'][] = array(
-              'local' => $local,
-              'rev'   => $rev,
-            );
-            break;
-          case 'branch':
-            $commit['branch'] = $value;
-            break;
-          case 'tag':
-            $commit['tag'] = $value;
-            break;
-          default:
-            throw new Exception("Unknown Mercurial log field '{$name}'!");
-        }
-      }
-      $result[] = $commit;
-    }
-
-    return $result;
-  }
-
   private function getWorkingCopyRevision() {
     // In Mercurial, "tip" means the tip of the current branch, not what's in
     // the working copy. The tip may be ahead of the working copy. We need to
diff --git a/src/repository/api/mercurial/__init__.php b/src/repository/api/mercurial/__init__.php
index f4ae19bc..4fad8a3a 100644
--- a/src/repository/api/mercurial/__init__.php
+++ b/src/repository/api/mercurial/__init__.php
@@ -10,6 +10,7 @@ phutil_require_module('arcanist', 'exception/usage');
 phutil_require_module('arcanist', 'parser/diff');
 phutil_require_module('arcanist', 'parser/diff/changetype');
 phutil_require_module('arcanist', 'repository/api/base');
+phutil_require_module('arcanist', 'repository/parser/mercurial');
 
 phutil_require_module('phutil', 'future/exec');
 phutil_require_module('phutil', 'utils');
diff --git a/src/repository/parser/mercurial/ArcanistMercurialParser.php b/src/repository/parser/mercurial/ArcanistMercurialParser.php
new file mode 100644
index 00000000..a5831e29
--- /dev/null
+++ b/src/repository/parser/mercurial/ArcanistMercurialParser.php
@@ -0,0 +1,192 @@
+<?php
+
+/*
+ * Copyright 2011 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Parses output from various "hg" commands into structured data. This class
+ * provides low-level APIs for reading "hg" output.
+ *
+ * @task  parse Parsing "hg" Output
+ * @group workingcopy
+ */
+final class ArcanistMercurialParser {
+
+
+/* -(  Parsing "hg" Output  )------------------------------------------------ */
+
+
+  /**
+   * Parse the output of "hg status".
+   *
+   * @param string The stdout from running an "hg status" command.
+   * @return dict Map of paths to ArcanistRepositoryAPI status flags.
+   * @task parse
+   */
+  public static function parseMercurialStatus($stdout) {
+    $result = array();
+
+    $stdout = trim($stdout);
+    if (!strlen($stdout)) {
+      return $result;
+    }
+
+    $lines = explode("\n", $stdout);
+    foreach ($lines as $line) {
+      $flags = 0;
+      list($code, $path) = explode(' ', $line, 2);
+      switch ($code) {
+        case 'A':
+          $flags |= ArcanistRepositoryAPI::FLAG_ADDED;
+          break;
+        case 'R':
+          $flags |= ArcanistRepositoryAPI::FLAG_REMOVED;
+          break;
+        case 'M':
+          $flags |= ArcanistRepositoryAPI::FLAG_MODIFIED;
+          break;
+        case 'C':
+          // This is "clean" and included only for completeness, these files
+          // have not been changed.
+          break;
+        case '!':
+          $flags |= ArcanistRepositoryAPI::FLAG_MISSING;
+          break;
+        case '?':
+          $flags |= ArcanistRepositoryAPI::FLAG_UNTRACKED;
+          break;
+        case 'I':
+          // This is "ignored" and included only for completeness.
+          break;
+        default:
+          throw new Exception("Unknown Mercurial status '{$code}'.");
+      }
+
+      $result[$path] = $flags;
+    }
+
+    return $result;
+  }
+
+
+  /**
+   * Parse the output of "hg log". This also parses "hg outgoing", "hg parents",
+   * and other similar commands. This assumes "--style default".
+   *
+   * @param string The stdout from running an "hg log" command.
+   * @return list List of dictionaries with commit information.
+   * @task parse
+   */
+  public static function parseMercurialLog($stdout) {
+    $result = array();
+
+    $stdout = trim($stdout);
+    if (!strlen($stdout)) {
+      return $result;
+    }
+
+    $chunks = explode("\n\n", $stdout);
+    foreach ($chunks as $chunk) {
+      $commit = array();
+      $lines = explode("\n", $chunk);
+      foreach ($lines as $line) {
+        if (preg_match('/^(comparing with|searching for changes)/', $line)) {
+          // These are sent to stdout when you run "hg outgoing" although the
+          // format is otherwise identical to "hg log".
+          continue;
+        }
+        list($name, $value) = explode(':', $line, 2);
+        $value = trim($value);
+        switch ($name) {
+          case 'user':
+            $commit['user'] = $value;
+            break;
+          case 'date':
+            $commit['date'] = strtotime($value);
+            break;
+          case 'summary':
+            $commit['summary'] = $value;
+            break;
+          case 'changeset':
+            list($local, $rev) = explode(':', $value, 2);
+            $commit['local'] = $local;
+            $commit['rev'] = $rev;
+            break;
+          case 'parent':
+            if (empty($commit['parents'])) {
+              $commit['parents'] = array();
+            }
+            list($local, $rev) = explode(':', $value, 2);
+            $commit['parents'][] = array(
+              'local' => $local,
+              'rev'   => $rev,
+            );
+            break;
+          case 'branch':
+            $commit['branch'] = $value;
+            break;
+          case 'tag':
+            $commit['tag'] = $value;
+            break;
+          default:
+            throw new Exception("Unknown Mercurial log field '{$name}'!");
+        }
+      }
+      $result[] = $commit;
+    }
+
+    return $result;
+  }
+
+
+  /**
+   * Parse the output of "hg branches".
+   *
+   * @param string The stdout from running an "hg branches" command.
+   * @return list A list of dictionaries with branch information.
+   * @task parse
+   */
+  public static function parseMercurialBranches($stdout) {
+    $lines = explode("\n", trim($stdout));
+
+    $branches = array();
+    foreach ($lines as $line) {
+      $matches = null;
+
+      // Output of "hg branches" normally looks like:
+      //
+      //  default                    15101:a21ccf4412d5
+      //
+      // ...but may also have human-readable cues like:
+      //
+      //  stable                     15095:ec222a29bdf0 (inactive)
+      //
+      // See the unit tests for more examples.
+      $regexp = '/^([^ ]+)\s+(\d+):([a-f0-9]+)(\s|$)/';
+
+      if (!preg_match($regexp, $line, $matches)) {
+        throw new Exception("Failed to parse 'hg branches' output: {$line}");
+      }
+      $branches[$matches[1]] = array(
+        'local'   => $matches[2],
+        'rev'     => $matches[3],
+      );
+    }
+
+    return $branches;
+  }
+
+}
diff --git a/src/repository/parser/mercurial/__init__.php b/src/repository/parser/mercurial/__init__.php
new file mode 100644
index 00000000..9de7b75e
--- /dev/null
+++ b/src/repository/parser/mercurial/__init__.php
@@ -0,0 +1,12 @@
+<?php
+/**
+ * This file is automatically generated. Lint this module to rebuild it.
+ * @generated
+ */
+
+
+
+phutil_require_module('arcanist', 'repository/api/base');
+
+
+phutil_require_source('ArcanistMercurialParser.php');
diff --git a/src/repository/parser/mercurial/__tests__/ArcanistMercurialParserTestCase.php b/src/repository/parser/mercurial/__tests__/ArcanistMercurialParserTestCase.php
new file mode 100644
index 00000000..939efdad
--- /dev/null
+++ b/src/repository/parser/mercurial/__tests__/ArcanistMercurialParserTestCase.php
@@ -0,0 +1,71 @@
+<?php
+
+/*
+ * Copyright 2011 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+final class ArcanistMercurialParserTestCase extends ArcanistPhutilTestCase {
+
+  public function testParseAll() {
+    $root = dirname(__FILE__).'/data/';
+    foreach (Filesystem::listDirectory($root) as $file) {
+      $this->parseData(
+        basename($file),
+        Filesystem::readFile($root.'/'.$file));
+    }
+  }
+
+  private function parseData($name, $data) {
+    switch ($name) {
+      case 'branches-basic.txt':
+        $output = ArcanistMercurialParser::parseMercurialBranches($data);
+        $this->assertEqual(
+          array('default', 'stable'),
+          array_keys($output));
+        $this->assertEqual(
+          array('a21ccf4412d5', 'ec222a29bdf0'),
+          array_values(ipull($output, 'rev')));
+        break;
+      case 'log-basic.txt':
+        $output = ArcanistMercurialParser::parseMercurialLog($data);
+        $this->assertEqual(
+          3,
+          count($output));
+        $this->assertEqual(
+          array('a21ccf4412d5', 'a051f8a6a7cc', 'b1f49efeab65'),
+          array_values(ipull($output, 'rev')));
+        break;
+      case 'log-empty.txt':
+        // Empty logs (e.g., "hg parents" for a root revision) should parse
+        // correctly.
+        $output = ArcanistMercurialParser::parseMercurialLog($data);
+        $this->assertEqual(
+          array(),
+          $output);
+        break;
+      case 'status-basic.txt':
+        $output = ArcanistMercurialParser::parseMercurialStatus($data);
+        $this->assertEqual(
+          4,
+          count($output));
+        $this->assertEqual(
+          array('changed', 'added', 'removed', 'untracked'),
+          array_keys($output));
+        break;
+      default:
+        throw new Exception("No test information for test data '{$name}'!");
+    }
+  }
+}
diff --git a/src/repository/parser/mercurial/__tests__/__init__.php b/src/repository/parser/mercurial/__tests__/__init__.php
new file mode 100644
index 00000000..254c2aba
--- /dev/null
+++ b/src/repository/parser/mercurial/__tests__/__init__.php
@@ -0,0 +1,16 @@
+<?php
+/**
+ * This file is automatically generated. Lint this module to rebuild it.
+ * @generated
+ */
+
+
+
+phutil_require_module('arcanist', 'repository/parser/mercurial');
+phutil_require_module('arcanist', 'unit/engine/phutil/testcase');
+
+phutil_require_module('phutil', 'filesystem');
+phutil_require_module('phutil', 'utils');
+
+
+phutil_require_source('ArcanistMercurialParserTestCase.php');
diff --git a/src/repository/parser/mercurial/__tests__/data/branches-basic.txt b/src/repository/parser/mercurial/__tests__/data/branches-basic.txt
new file mode 100644
index 00000000..706ac29c
--- /dev/null
+++ b/src/repository/parser/mercurial/__tests__/data/branches-basic.txt
@@ -0,0 +1,2 @@
+default                    15101:a21ccf4412d5
+stable                     15095:ec222a29bdf0 (inactive)
diff --git a/src/repository/parser/mercurial/__tests__/data/log-basic.txt b/src/repository/parser/mercurial/__tests__/data/log-basic.txt
new file mode 100644
index 00000000..4997f328
--- /dev/null
+++ b/src/repository/parser/mercurial/__tests__/data/log-basic.txt
@@ -0,0 +1,16 @@
+changeset:   15101:a21ccf4412d5
+tag:         tip
+user:        Greg Ward <greg@gerg.ca>
+date:        Wed Sep 14 22:28:27 2011 -0400
+summary:     share: allow trailing newline on .hg/sharedpath.
+
+changeset:   15100:a051f8a6a7cc
+user:        Ben Hockey <neonstalwart@gmail.com>
+date:        Wed Sep 07 10:24:26 2011 -0400
+summary:     contrib: some support for named branches in zsh_completion (issue2988)
+
+changeset:   15099:b1f49efeab65
+user:        Simon Heimberg <simohe@besonet.ch>
+date:        Wed Sep 14 17:06:33 2011 +0200
+summary:     test: test for options duplicate with global options
+
diff --git a/src/repository/parser/mercurial/__tests__/data/log-empty.txt b/src/repository/parser/mercurial/__tests__/data/log-empty.txt
new file mode 100644
index 00000000..8b137891
--- /dev/null
+++ b/src/repository/parser/mercurial/__tests__/data/log-empty.txt
@@ -0,0 +1 @@
+
diff --git a/src/repository/parser/mercurial/__tests__/data/status-basic.txt b/src/repository/parser/mercurial/__tests__/data/status-basic.txt
new file mode 100644
index 00000000..c49407f2
--- /dev/null
+++ b/src/repository/parser/mercurial/__tests__/data/status-basic.txt
@@ -0,0 +1,4 @@
+M changed
+A added
+! removed
+? untracked