Refactor commit ranges and base commit handling

Summary:
See D4049, D4096.

  - Move commit range storage from Mercurial and Git APIs to the base API.
  - Move caching up to the base level.
    - Store symbolic name and resolved name separately, so we can re-resolve the correct commit from the symbolic name after dirtying caches.
  - Rename `supportsRelativeLocalCommit()` to `supportsCommitRanges()` (old name wasn't very good, and not consistent with new terminology like the `--base` flag).
  - Rename `getRelativeCommit()` and `setRelativeCommit()` to `getBaseCommit()` and `setBaseCommit()`.
  - Introduce `reloadCommitRange()` and call it from `reloadWorkingCopy()`.

I think this fixes the problem in D4049, and provides a general solution for the class of problems we're running into here, with D4096. Specifically:

  - We no longer get dirty caches, as long as you call reloadWorkingCopy() after changing the working copy (or call a method which calls it for you).
  - We no longer get order-of-parsing-things problems, because setBaseCommit() reloads the appropriate caches.
  - We no longer get nasty effects from calling `requireCleanWorkingCopy()` too early.

Test Plan: This is pretty far-reaching and hard to test. Unit tests; ran various arc commands. :/

Reviewers: vrana

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D4097

src/repository/api/ArcanistGitAPI.php

@@ -7,7 +7,6 @@
  */
 final class ArcanistGitAPI extends ArcanistRepositoryAPI {
 
-  private $relativeCommit = null;
   private $repositoryHasNoCommits = false;
   const SEARCH_LENGTH_FOR_PARENT_REVISIONS = 16;
 
@@ -43,18 +42,13 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
     return !$this->repositoryHasNoCommits;
   }
 
-  public function setRelativeCommit($relative_commit) {
-    $this->relativeCommit = $relative_commit;
-    return $this;
-  }
-
   public function getLocalCommitInformation() {
     if ($this->repositoryHasNoCommits) {
       // Zero commits.
       throw new Exception(
         "You can't get local commit information for a repository with no ".
         "commits.");
-    } else if ($this->relativeCommit == self::GIT_MAGIC_ROOT_COMMIT) {
+    } else if ($this->getBaseCommit() == self::GIT_MAGIC_ROOT_COMMIT) {
       // One commit.
       $against = 'HEAD';
     } else {
@@ -79,7 +73,7 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
       // this as being the commits X and Y. If we log "B..Y", we only show
       // Y. With "Y --not B", we show X and Y.
 
-      $against = csprintf('%s --not %s', 'HEAD', $this->getRelativeCommit());
+      $against = csprintf('%s --not %s', 'HEAD', $this->getBaseCommit());
     }
 
     // NOTE: Windows escaping of "%" symbols apparently is inherently broken;
@@ -124,139 +118,153 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
     return $commits;
   }
 
-  public function getRelativeCommit() {
+  protected function buildBaseCommit($symbolic_commit) {
-    if ($this->relativeCommit === null) {
+    if ($symbolic_commit !== null) {
-
+      if ($symbolic_commit == ArcanistGitAPI::GIT_MAGIC_ROOT_COMMIT) {
-      // Detect zero-commit or one-commit repositories. There is only one
-      // relative-commit value that makes any sense in these repositories: the
-      // empty tree.
-      list($err) = $this->execManualLocal('rev-parse --verify HEAD^');
-      if ($err) {
-        list($err) = $this->execManualLocal('rev-parse --verify HEAD');
-        if ($err) {
-          $this->repositoryHasNoCommits = true;
-        }
-
-        $this->relativeCommit = self::GIT_MAGIC_ROOT_COMMIT;
-
-        if ($this->repositoryHasNoCommits) {
-          $this->setBaseCommitExplanation(
-            "the repository has no commits.");
-        } else {
-          $this->setBaseCommitExplanation(
-            "the repository has only one commit.");
-        }
-
-        return $this->relativeCommit;
-      }
-
-      if ($this->getBaseCommitArgumentRules() ||
-          $this->getWorkingCopyIdentity()->getConfigFromAnySource('base')) {
-        $base = $this->resolveBaseCommit();
-        if (!$base) {
-          throw new ArcanistUsageException(
-            "None of the rules in your 'base' configuration matched a valid ".
-            "commit. Adjust rules or specify which commit you want to use ".
-            "explicitly.");
-        }
-        $this->relativeCommit = $base;
-        return $this->relativeCommit;
-      }
-
-      $do_write = false;
-      $default_relative = null;
-      $working_copy = $this->getWorkingCopyIdentity();
-      if ($working_copy) {
-        $default_relative = $working_copy->getConfig(
-          'git.default-relative-commit');
         $this->setBaseCommitExplanation(
-          "it is the merge-base of '{$default_relative}' and HEAD, as ".
+          "you explicitly specified the empty tree.");
-          "specified in 'git.default-relative-commit' in '.arcconfig'. This ".
+        return $symbolic_commit;
-          "setting overrides other settings.");
       }
 
-      if (!$default_relative) {
+      list($err, $merge_base) = $this->execManualLocal(
-        list($err, $upstream) = $this->execManualLocal(
-          "rev-parse --abbrev-ref --symbolic-full-name '@{upstream}'");
-
-        if (!$err) {
-          $default_relative = trim($upstream);
-          $this->setBaseCommitExplanation(
-            "it is the merge-base of '{$default_relative}' (the Git upstream ".
-            "of the current branch) HEAD.");
-        }
-      }
-
-      if (!$default_relative) {
-        $default_relative = $this->readScratchFile('default-relative-commit');
-        $default_relative = trim($default_relative);
-        if ($default_relative) {
-          $this->setBaseCommitExplanation(
-            "it is the merge-base of '{$default_relative}' and HEAD, as ".
-            "specified in '.git/arc/default-relative-commit'.");
-        }
-      }
-
-      if (!$default_relative) {
-
-        // TODO: Remove the history lesson soon.
-
-        echo phutil_console_format(
-          "<bg:green>** Select a Default Commit Range **</bg>\n\n");
-        echo phutil_console_wrap(
-          "You're running a command which operates on a range of revisions ".
-          "(usually, from some revision to HEAD) but have not specified the ".
-          "revision that should determine the start of the range.\n\n".
-          "Previously, arc assumed you meant 'HEAD^' when you did not specify ".
-          "a start revision, but this behavior does not make much sense in ".
-          "most workflows outside of Facebook's historic git-svn workflow.\n\n".
-          "arc no longer assumes 'HEAD^'. You must specify a relative commit ".
-          "explicitly when you invoke a command (e.g., `arc diff HEAD^`, not ".
-          "just `arc diff`) or select a default for this working copy.\n\n".
-          "In most cases, the best default is 'origin/master'. You can also ".
-          "select 'HEAD^' to preserve the old behavior, or some other remote ".
-          "or branch. But you almost certainly want to select ".
-          "'origin/master'.\n\n".
-          "(Technically: the merge-base of the selected revision and HEAD is ".
-          "used to determine the start of the commit range.)");
-
-        $prompt = "What default do you want to use? [origin/master]";
-        $default = phutil_console_prompt($prompt);
-
-        if (!strlen(trim($default))) {
-          $default = 'origin/master';
-        }
-
-        $default_relative = $default;
-        $do_write = true;
-      }
-
-      list($object_type) = $this->execxLocal(
-        'cat-file -t %s',
-        $default_relative);
-
-      if (trim($object_type) !== 'commit') {
-        throw new Exception(
-          "Relative commit '{$default_relative}' is not the name of a commit!");
-      }
-
-      if ($do_write) {
-        // Don't perform this write until we've verified that the object is a
-        // valid commit name.
-        $this->writeScratchFile('default-relative-commit', $default_relative);
-        $this->setBaseCommitExplanation(
-          "it is the merge-base of '{$default_relative}' and HEAD, as you ".
-          "just specified.");
-      }
-
-      list($merge_base) = $this->execxLocal(
         'merge-base %s HEAD',
-        $default_relative);
+        $symbolic_commit);
+      if ($err) {
+        throw new ArcanistUsageException(
+          "Unable to find any git commit named '{$symbolic_commit}' in ".
+          "this repository.");
+      }
 
-      $this->relativeCommit = trim($merge_base);
+      $this->setBaseCommitExplanation(
+        "it is the merge-base of '{$symbolic_commit}' and HEAD, as you ".
+        "explicitly specified.");
+      return trim($merge_base);
     }
 
-    return $this->relativeCommit;
+    // Detect zero-commit or one-commit repositories. There is only one
+    // relative-commit value that makes any sense in these repositories: the
+    // empty tree.
+    list($err) = $this->execManualLocal('rev-parse --verify HEAD^');
+    if ($err) {
+      list($err) = $this->execManualLocal('rev-parse --verify HEAD');
+      if ($err) {
+        $this->repositoryHasNoCommits = true;
+      }
+
+      if ($this->repositoryHasNoCommits) {
+        $this->setBaseCommitExplanation(
+          "the repository has no commits.");
+      } else {
+        $this->setBaseCommitExplanation(
+          "the repository has only one commit.");
+      }
+
+      return self::GIT_MAGIC_ROOT_COMMIT;
+    }
+
+    if ($this->getBaseCommitArgumentRules() ||
+        $this->getWorkingCopyIdentity()->getConfigFromAnySource('base')) {
+      $base = $this->resolveBaseCommit();
+      if (!$base) {
+        throw new ArcanistUsageException(
+          "None of the rules in your 'base' configuration matched a valid ".
+          "commit. Adjust rules or specify which commit you want to use ".
+          "explicitly.");
+      }
+      return $base;
+    }
+
+    $do_write = false;
+    $default_relative = null;
+    $working_copy = $this->getWorkingCopyIdentity();
+    if ($working_copy) {
+      $default_relative = $working_copy->getConfig(
+        'git.default-relative-commit');
+      $this->setBaseCommitExplanation(
+        "it is the merge-base of '{$default_relative}' and HEAD, as ".
+        "specified in 'git.default-relative-commit' in '.arcconfig'. This ".
+        "setting overrides other settings.");
+    }
+
+    if (!$default_relative) {
+      list($err, $upstream) = $this->execManualLocal(
+        "rev-parse --abbrev-ref --symbolic-full-name '@{upstream}'");
+
+      if (!$err) {
+        $default_relative = trim($upstream);
+        $this->setBaseCommitExplanation(
+          "it is the merge-base of '{$default_relative}' (the Git upstream ".
+          "of the current branch) HEAD.");
+      }
+    }
+
+    if (!$default_relative) {
+      $default_relative = $this->readScratchFile('default-relative-commit');
+      $default_relative = trim($default_relative);
+      if ($default_relative) {
+        $this->setBaseCommitExplanation(
+          "it is the merge-base of '{$default_relative}' and HEAD, as ".
+          "specified in '.git/arc/default-relative-commit'.");
+      }
+    }
+
+    if (!$default_relative) {
+
+      // TODO: Remove the history lesson soon.
+
+      echo phutil_console_format(
+        "<bg:green>** Select a Default Commit Range **</bg>\n\n");
+      echo phutil_console_wrap(
+        "You're running a command which operates on a range of revisions ".
+        "(usually, from some revision to HEAD) but have not specified the ".
+        "revision that should determine the start of the range.\n\n".
+        "Previously, arc assumed you meant 'HEAD^' when you did not specify ".
+        "a start revision, but this behavior does not make much sense in ".
+        "most workflows outside of Facebook's historic git-svn workflow.\n\n".
+        "arc no longer assumes 'HEAD^'. You must specify a relative commit ".
+        "explicitly when you invoke a command (e.g., `arc diff HEAD^`, not ".
+        "just `arc diff`) or select a default for this working copy.\n\n".
+        "In most cases, the best default is 'origin/master'. You can also ".
+        "select 'HEAD^' to preserve the old behavior, or some other remote ".
+        "or branch. But you almost certainly want to select ".
+        "'origin/master'.\n\n".
+        "(Technically: the merge-base of the selected revision and HEAD is ".
+        "used to determine the start of the commit range.)");
+
+      $prompt = "What default do you want to use? [origin/master]";
+      $default = phutil_console_prompt($prompt);
+
+      if (!strlen(trim($default))) {
+        $default = 'origin/master';
+      }
+
+      $default_relative = $default;
+      $do_write = true;
+    }
+
+    list($object_type) = $this->execxLocal(
+      'cat-file -t %s',
+      $default_relative);
+
+    if (trim($object_type) !== 'commit') {
+      throw new Exception(
+        "Relative commit '{$default_relative}' is not the name of a commit!");
+    }
+
+    if ($do_write) {
+      // Don't perform this write until we've verified that the object is a
+      // valid commit name.
+      $this->writeScratchFile('default-relative-commit', $default_relative);
+      $this->setBaseCommitExplanation(
+        "it is the merge-base of '{$default_relative}' and HEAD, as you ".
+        "just specified.");
+    }
+
+    list($merge_base) = $this->execxLocal(
+      'merge-base %s HEAD',
+      $default_relative);
+
+    return trim($merge_base);
   }
 
   private function getDiffFullOptions($detect_moves_and_renames = true) {
@@ -294,7 +302,7 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
     $options = $this->getDiffFullOptions();
     list($stdout) = $this->execxLocal(
       "diff {$options} %s --",
-      $this->getRelativeCommit());
+      $this->getBaseCommit());
     return $stdout;
   }
 
@@ -308,7 +316,7 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
     $options = $this->getDiffFullOptions($detect_moves_and_renames);
     list($stdout) = $this->execxLocal(
       "diff {$options} %s -- %s",
-      $this->getRelativeCommit(),
+      $this->getBaseCommit(),
       $path);
     return $stdout;
   }
@@ -336,7 +344,7 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
   }
 
   public function getGitCommitLog() {
-    $relative = $this->getRelativeCommit();
+    $relative = $this->getBaseCommit();
     if ($this->repositoryHasNoCommits) {
       // No commits yet.
       return '';
@@ -348,7 +356,7 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
       // 2..N commits.
       list($stdout) = $this->execxLocal(
         'log --first-parent --format=medium %s..HEAD',
-        $this->getRelativeCommit());
+        $this->getBaseCommit());
     }
     return $stdout;
   }
@@ -357,14 +365,14 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
     list($stdout) = $this->execxLocal(
       'log --format=medium -n%d %s',
       self::SEARCH_LENGTH_FOR_PARENT_REVISIONS,
-      $this->getRelativeCommit());
+      $this->getBaseCommit());
     return $stdout;
   }
 
   public function getSourceControlBaseRevision() {
     list($stdout) = $this->execxLocal(
       'rev-parse %s',
-      $this->getRelativeCommit());
+      $this->getBaseCommit());
     return rtrim($stdout, "\n");
   }
 
@@ -455,7 +463,7 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
     list($stdout, $stderr) = $this->execxLocal(
       'diff %C --raw %s --',
       $this->getDiffBaseOptions(),
-      $this->getRelativeCommit());
+      $this->getBaseCommit());
 
     return $this->parseGitStatus($stdout);
   }
@@ -477,6 +485,8 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
     $this->execxLocal(
       'add -- %Ls',
       $paths);
+    $this->reloadWorkingCopy();
+    return $this;
   }
 
   public function doCommit($message) {
@@ -497,6 +507,8 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
     $this->execxLocal(
       'commit --amend --allow-empty -F %s',
       $tmp_file);
+    $this->reloadWorkingCopy();
+    return $this;
   }
 
   public function getPreReceiveHookStatus($old_ref, $new_ref) {
@@ -563,7 +575,7 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
     // TODO: 'git blame' supports --porcelain and we should probably use it.
     list($stdout) = $this->execxLocal(
       'blame --date=iso -w -M %s -- %s',
-      $this->getRelativeCommit(),
+      $this->getBaseCommit(),
       $path);
 
     $blame = array();
@@ -597,7 +609,7 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
   }
 
   public function getOriginalFileData($path) {
-    return $this->getFileDataAtRevision($path, $this->getRelativeCommit());
+    return $this->getFileDataAtRevision($path, $this->getBaseCommit());
   }
 
   public function getCurrentFileData($path) {
@@ -711,7 +723,11 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
     return true;
   }
 
-  public function supportsRelativeLocalCommits() {
+  public function supportsCommitRanges() {
+    return true;
+  }
+
+  public function supportsLocalCommits() {
     return true;
   }
 
@@ -726,33 +742,6 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
     return true;
   }
 
-  public function parseRelativeLocalCommit(array $argv) {
-    if (count($argv) == 0) {
-      return;
-    }
-    if (count($argv) != 1) {
-      throw new ArcanistUsageException("Specify only one commit.");
-    }
-    $base = reset($argv);
-    if ($base == ArcanistGitAPI::GIT_MAGIC_ROOT_COMMIT) {
-      $merge_base = $base;
-      $this->setBaseCommitExplanation(
-        "you explicitly specified the empty tree.");
-    } else {
-      list($err, $merge_base) = $this->execManualLocal(
-        'merge-base %s HEAD',
-        $base);
-      if ($err) {
-        throw new ArcanistUsageException(
-          "Unable to find any git commit named '{$base}' in this repository.");
-      }
-      $this->setBaseCommitExplanation(
-        "it is the merge-base of '{$base}' and HEAD, as you explicitly ".
-        "specified.");
-    }
-    $this->setRelativeCommit(trim($merge_base));
-  }
-
   public function getAllLocalChanges() {
     $diff = $this->getFullGitDiff();
     if (!strlen(trim($diff))) {
@@ -859,6 +848,7 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
 
   public function updateWorkingCopy() {
     $this->execxLocal('pull');
+    $this->reloadWorkingCopy();
   }
 
   public function getCommitSummary($commit) {

src/repository/api/ArcanistMercurialAPI.php

@@ -7,10 +7,7 @@
  */
 final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
 
-  private $base;
-  private $relativeCommit;
   private $branch;
-  private $workingCopyRevision;
   private $localCommitInfo;
   private $includeDirectoryStateInDiffs;
   private $rawDiffCache = array();
@@ -58,7 +55,7 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
   }
 
   public function getSourceControlBaseRevision() {
-    return $this->getCanonicalRevisionName($this->getRelativeCommit());
+    return $this->getCanonicalRevisionName($this->getBaseCommit());
   }
 
   public function getCanonicalRevisionName($string) {
@@ -81,107 +78,99 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
     return $this->branch;
   }
 
-  public function setRelativeCommit($commit) {
+  public function didReloadCommitRange() {
-    try {
-      $commit = $this->getCanonicalRevisionName($commit);
-    } catch (Exception $ex) {
-      throw new ArcanistUsageException(
-        "Commit '{$commit}' is not a valid Mercurial commit identifier.");
-    }
-
-    $this->relativeCommit = $commit;
-    $this->status = null;
     $this->localCommitInfo = null;
-
-    return $this;
   }
 
-  public function getRelativeCommit() {
+  protected function buildBaseCommit($symbolic_commit) {
-    if (empty($this->relativeCommit)) {
+    if ($symbolic_commit !== null) {
-
+      try {
-      if ($this->getBaseCommitArgumentRules() ||
+        $commit = $this->getCanonicalRevisionName($commit);
-          $this->getWorkingCopyIdentity()->getConfigFromAnySource('base')) {
+      } catch (Exception $ex) {
-        $base = $this->resolveBaseCommit();
+        throw new ArcanistUsageException(
-        if (!$base) {
+          "Commit '{$commit}' is not a valid Mercurial commit identifier.");
-          throw new ArcanistUsageException(
-            "None of the rules in your 'base' configuration matched a valid ".
-            "commit. Adjust rules or specify which commit you want to use ".
-            "explicitly.");
-        }
-        $this->relativeCommit = $base;
-        return $this->relativeCommit;
       }
-
+      $this->setBaseCommitExplanation("you specified it explicitly.");
-      list($err, $stdout) = $this->execManualLocal(
+      return $commit;
-        'outgoing --branch %s --style default',
-        $this->getBranchName());
-
-      if (!$err) {
-        $logs = ArcanistMercurialParser::parseMercurialLog($stdout);
-      } else {
-        // Mercurial (in some versions?) raises an error when there's nothing
-        // outgoing.
-        $logs = array();
-      }
-
-      if (!$logs) {
-
-        $this->setBaseCommitExplanation(
-          "you have no outgoing commits, so arc assumes you intend to submit ".
-          "uncommitted changes in the working copy.");
-        // In Mercurial, we support operations against uncommitted changes.
-        $this->setRelativeCommit($this->getWorkingCopyRevision());
-        return $this->relativeCommit;
-      }
-
-      $outgoing_revs = ipull($logs, 'rev');
-
-      // This is essentially an implementation of a theoretical `hg merge-base`
-      // command.
-      $against = $this->getWorkingCopyRevision();
-      while (true) {
-        // NOTE: The "^" and "~" syntaxes were only added in hg 1.9, which is
-        // new as of July 2011, so do this in a compatible way. Also, "hg log"
-        // and "hg outgoing" don't necessarily show parents (even if given an
-        // explicit template consisting of just the parents token) so we need
-        // to separately execute "hg parents".
-
-        list($stdout) = $this->execxLocal(
-          'parents --style default --rev %s',
-          $against);
-        $parents_logs = ArcanistMercurialParser::parseMercurialLog($stdout);
-
-        list($p1, $p2) = array_merge($parents_logs, array(null, null));
-
-        if ($p1 && !in_array($p1['rev'], $outgoing_revs)) {
-          $against = $p1['rev'];
-          break;
-        } else if ($p2 && !in_array($p2['rev'], $outgoing_revs)) {
-          $against = $p2['rev'];
-          break;
-        } else if ($p1) {
-          $against = $p1['rev'];
-        } else {
-          // This is the case where you have a new repository and the entire
-          // thing is outgoing; Mercurial literally accepts "--rev null" as
-          // meaning "diff against the empty state".
-          $against = 'null';
-          break;
-        }
-      }
-
-      if ($against == 'null') {
-        $this->setBaseCommitExplanation(
-          "this is a new repository (all changes are outgoing).");
-      } else {
-        $this->setBaseCommitExplanation(
-          "it is the first commit reachable from the working copy state ".
-          "which is not outgoing.");
-      }
-
-      $this->setRelativeCommit($against);
     }
-    return $this->relativeCommit;
+
+    if ($this->getBaseCommitArgumentRules() ||
+        $this->getWorkingCopyIdentity()->getConfigFromAnySource('base')) {
+      $base = $this->resolveBaseCommit();
+      if (!$base) {
+        throw new ArcanistUsageException(
+          "None of the rules in your 'base' configuration matched a valid ".
+          "commit. Adjust rules or specify which commit you want to use ".
+          "explicitly.");
+      }
+      return $base;
+    }
+
+    list($err, $stdout) = $this->execManualLocal(
+      'outgoing --branch %s --style default',
+      $this->getBranchName());
+
+    if (!$err) {
+      $logs = ArcanistMercurialParser::parseMercurialLog($stdout);
+    } else {
+      // Mercurial (in some versions?) raises an error when there's nothing
+      // outgoing.
+      $logs = array();
+    }
+
+    if (!$logs) {
+      $this->setBaseCommitExplanation(
+        "you have no outgoing commits, so arc assumes you intend to submit ".
+        "uncommitted changes in the working copy.");
+      return $this->getWorkingCopyRevision();
+    }
+
+    $outgoing_revs = ipull($logs, 'rev');
+
+    // This is essentially an implementation of a theoretical `hg merge-base`
+    // command.
+    $against = $this->getWorkingCopyRevision();
+    while (true) {
+      // NOTE: The "^" and "~" syntaxes were only added in hg 1.9, which is
+      // new as of July 2011, so do this in a compatible way. Also, "hg log"
+      // and "hg outgoing" don't necessarily show parents (even if given an
+      // explicit template consisting of just the parents token) so we need
+      // to separately execute "hg parents".
+
+      list($stdout) = $this->execxLocal(
+        'parents --style default --rev %s',
+        $against);
+      $parents_logs = ArcanistMercurialParser::parseMercurialLog($stdout);
+
+      list($p1, $p2) = array_merge($parents_logs, array(null, null));
+
+      if ($p1 && !in_array($p1['rev'], $outgoing_revs)) {
+        $against = $p1['rev'];
+        break;
+      } else if ($p2 && !in_array($p2['rev'], $outgoing_revs)) {
+        $against = $p2['rev'];
+        break;
+      } else if ($p1) {
+        $against = $p1['rev'];
+      } else {
+        // This is the case where you have a new repository and the entire
+        // thing is outgoing; Mercurial literally accepts "--rev null" as
+        // meaning "diff against the empty state".
+        $against = 'null';
+        break;
+      }
+    }
+
+    if ($against == 'null') {
+      $this->setBaseCommitExplanation(
+        "this is a new repository (all changes are outgoing).");
+    } else {
+      $this->setBaseCommitExplanation(
+        "it is the first commit reachable from the working copy state ".
+        "which is not outgoing.");
+    }
+
+    return $against;
   }
 
   public function getLocalCommitInformation() {
@@ -190,7 +179,7 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
         "log --template '%C' --rev %s --branch %s --",
         "{node}\1{rev}\1{author}\1{date|rfc822date}\1".
           "{branch}\1{tag}\1{parents}\1{desc}\2",
-        '(ancestors(.) - ancestors('.$this->getRelativeCommit().'))',
+        '(ancestors(.) - ancestors('.$this->getBaseCommit().'))',
         $this->getBranchName());
       $logs = array_filter(explode("\2", $info));
 
@@ -271,7 +260,7 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
   public function getBlame($path) {
     list($stdout) = $this->execxLocal(
       'annotate -u -v -c --rev %s -- %s',
-      $this->getRelativeCommit(),
+      $this->getBaseCommit(),
       $path);
 
     $blame = array();
@@ -355,6 +344,7 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
     // Diffs are against ".", so we need to drop the cache if we change the
     // working copy.
     $this->rawDiffCache = array();
+    $this->branch = null;
   }
 
   private function getDiffOptions() {
@@ -373,7 +363,7 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
     // copy commit" (i.e., from 'x' to '.'). The latter excludes any dirty
     // changes in the working copy.
 
-    $range = $this->getRelativeCommit();
+    $range = $this->getBaseCommit();
     if (!$this->includeDirectoryStateInDiffs) {
       $range .= '...';
     }
@@ -399,7 +389,7 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
   }
 
   public function getOriginalFileData($path) {
-    return $this->getFileDataAtRevision($path, $this->getRelativeCommit());
+    return $this->getFileDataAtRevision($path, $this->getBaseCommit());
   }
 
   public function getCurrentFileData($path) {
@@ -438,7 +428,11 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
     }
   }
 
-  public function supportsRelativeLocalCommits() {
+  public function supportsCommitRanges() {
+    return true;
+  }
+
+  public function supportsLocalCommits() {
     return true;
   }
 
@@ -458,21 +452,6 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
     return $message;
   }
 
-  public function parseRelativeLocalCommit(array $argv) {
-    if (count($argv) == 0) {
-      return;
-    }
-    if (count($argv) != 1) {
-      throw new ArcanistUsageException("Specify only one commit.");
-    }
-
-    $this->setBaseCommitExplanation("you explicitly specified it.");
-
-    // This does the "hg id" call we need to normalize/validate the revision
-    // identifier.
-    $this->setRelativeCommit(reset($argv));
-  }
-
   public function getAllLocalChanges() {
     $diff = $this->getFullMercurialDiff();
     if (!strlen(trim($diff))) {
@@ -513,7 +492,7 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
   public function getCommitMessageLog() {
     list($stdout) = $this->execxLocal(
       "log --template '{node}\\2{desc}\\1' --rev %s --branch %s --",
-      'ancestors(.) - ancestors('.$this->getRelativeCommit().')',
+      'ancestors(.) - ancestors('.$this->getBaseCommit().')',
       $this->getBranchName());
 
     $map = array();
@@ -593,6 +572,7 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
 
   public function updateWorkingCopy() {
     $this->execxLocal('up');
+    $this->reloadWorkingCopy();
   }
 
   private function getMercurialConfig($key, $default = null) {
@@ -611,6 +591,7 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
     $this->execxLocal(
       'add -- %Ls',
       $paths);
+    $this->reloadWorkingCopy();
   }
 
   public function doCommit($message) {
@@ -628,6 +609,7 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
     $this->execxLocal(
       'commit --amend -l %s',
       $tmp_file);
+    $this->reloadWorkingCopy();
   }
 
   public function setIncludeDirectoryStateInDiffs($include) {

src/repository/api/ArcanistRepositoryAPI.php

@@ -34,6 +34,9 @@ abstract class ArcanistRepositoryAPI {
   private $uncommittedStatusCache;
   private $commitRangeStatusCache;
 
+  private $symbolicBaseCommit;
+  private $resolvedBaseCommit;
+
   abstract public function getSourceControlSystemName();
 
   public function getDiffLinesOfContext() {
@@ -257,6 +260,7 @@ abstract class ArcanistRepositoryAPI {
     $this->commitRangeStatusCache = null;
 
     $this->didReloadWorkingCopy();
+    $this->reloadCommitRange();
 
     return $this;
   }
@@ -310,7 +314,6 @@ abstract class ArcanistRepositoryAPI {
   abstract public function getSourceControlPath();
   abstract public function isHistoryDefaultImmutable();
   abstract public function supportsAmend();
-  abstract public function supportsRelativeLocalCommits();
   abstract public function getWorkingCopyRevision();
   abstract public function updateWorkingCopy();
   abstract public function getMetadataPath();
@@ -334,6 +337,8 @@ abstract class ArcanistRepositoryAPI {
     throw new ArcanistCapabilityNotSupportedException($this);
   }
 
+  abstract public function supportsLocalCommits();
+
   public function doCommit($message) {
     throw new ArcanistCapabilityNotSupportedException($this);
   }
@@ -355,10 +360,6 @@ abstract class ArcanistRepositoryAPI {
     throw new ArcanistCapabilityNotSupportedException($this);
   }
 
-  public function parseRelativeLocalCommit(array $argv) {
-    throw new ArcanistCapabilityNotSupportedException($this);
-  }
-
   public function getCommitSummary($commit) {
     throw new ArcanistCapabilityNotSupportedException($this);
   }
@@ -539,6 +540,47 @@ abstract class ArcanistRepositoryAPI {
 
 /* -(  Base Commits  )------------------------------------------------------- */
 
+  abstract public function supportsCommitRanges();
+
+  final public function setBaseCommit($symbolic_commit) {
+    if (!$this->supportsCommitRanges()) {
+      throw new ArcanistCapabilityNotSupportedException($this);
+    }
+
+    $this->symbolicBaseCommit = $symbolic_commit;
+    $this->reloadCommitRange();
+    return $this;
+  }
+
+  final public function getBaseCommit() {
+    if (!$this->supportsCommitRanges()) {
+      throw new ArcanistCapabilityNotSupportedException($this);
+    }
+
+    if ($this->resolvedBaseCommit === null) {
+      $commit = $this->buildBaseCommit($this->symbolicBaseCommit);
+      $this->resolvedBaseCommit = $commit;
+    }
+
+    return $this->resolvedBaseCommit;
+  }
+
+  final public function reloadCommitRange() {
+    $this->resolvedBaseCommit = null;
+    $this->baseCommitExplanation = null;
+
+    $this->didReloadCommitRange();
+
+    return $this;
+  }
+
+  protected function didReloadCommitRange() {
+    return;
+  }
+
+  protected function buildBaseCommit($symbolic_commit) {
+    throw new ArcanistCapabilityNotSupportedException($this);
+  }
 
   public function getBaseCommitExplanation() {
     return $this->baseCommitExplanation;

src/repository/api/ArcanistSubversionAPI.php

@@ -553,7 +553,11 @@ EODIFF;
     return false;
   }
 
-  public function supportsRelativeLocalCommits() {
+  public function supportsCommitRanges() {
+    return false;
+  }
+
+  public function supportsLocalCommits() {
     return false;
   }
 

src/workflow/ArcanistBaseWorkflow.php

@@ -828,7 +828,7 @@ abstract class ArcanistBaseWorkflow {
       if ($this->shouldAmend) {
         $commit = head($api->getLocalCommitInformation());
         $api->amendCommit($commit['message']);
-      } else if ($api->supportsRelativeLocalCommits()) {
+      } else if ($api->supportsLocalCommits()) {
         $api->doCommit(self::AUTO_COMMIT_TITLE);
       }
     }
@@ -982,7 +982,12 @@ abstract class ArcanistBaseWorkflow {
   protected function getChange($path) {
     $repository_api = $this->getRepositoryAPI();
 
-    if ($repository_api instanceof ArcanistSubversionAPI) {
+    // TODO: Very gross
+    $is_git = ($repository_api instanceof ArcanistGitAPI);
+    $is_hg = ($repository_api instanceof ArcanistMercurialAPI);
+    $is_svn = ($repository_api instanceof ArcanistSubversionAPI);
+
+    if ($is_svn) {
       // NOTE: In SVN, we don't currently support a "get all local changes"
       // operation, so special case it.
       if (empty($this->changeCache[$path])) {
@@ -994,7 +999,7 @@ abstract class ArcanistBaseWorkflow {
         }
         $this->changeCache[$path] = reset($changes);
       }
-    } else if ($repository_api->supportsRelativeLocalCommits()) {
+    } else if ($is_git || $is_hg) {
       if (empty($this->changeCache)) {
         $changes = $repository_api->getAllLocalChanges();
         foreach ($changes as $change) {
@@ -1006,7 +1011,7 @@ abstract class ArcanistBaseWorkflow {
     }
 
     if (empty($this->changeCache[$path])) {
-      if ($repository_api instanceof ArcanistGitAPI) {
+      if ($is_git) {
         // This can legitimately occur under git if you make a change, "git
         // commit" it, and then revert the change in the working copy and run
         // "arc lint".
@@ -1257,9 +1262,7 @@ abstract class ArcanistBaseWorkflow {
       }
     } else {
       $repository_api = $this->getRepositoryAPI();
-      if ($rev) {
+      $this->parseBaseCommitArgument(array($rev));
-        $repository_api->parseRelativeLocalCommit(array($rev));
-      }
 
       $paths = $repository_api->getWorkingCopyStatus();
       foreach ($paths as $path => $flags) {
@@ -1492,4 +1495,26 @@ abstract class ArcanistBaseWorkflow {
     return $event;
   }
 
+  public function parseBaseCommitArgument(array $argv) {
+    if (!count($argv)) {
+      return;
+    }
+
+    $api = $this->getRepositoryAPI();
+    if (!$api->supportsCommitRanges()) {
+      throw new ArcanistUsageException(
+        "This version control system does not support commit ranges.");
+    }
+
+    if (count($argv) > 1) {
+      throw new ArcanistUsageException(
+        "Specify exactly one base commit. The end of the commit range is ".
+        "always the working copy state.");
+    }
+
+    $api->setBaseCommit(head($argv));
+
+    return $this;
+  }
+
 }

src/workflow/ArcanistCoverWorkflow.php

@@ -70,9 +70,7 @@ EOTEXT
     $in_rev = $this->getArgument('rev');
 
     if ($in_rev) {
-      // Although selectPathsForWorkflow() may set this, we want to set it
+      $this->parseBaseCommitArgument(array($in_rev));
-      // explicitly so we blame against the correct relative commit.
-      $repository_api->parseRelativeLocalCommit(array($in_rev));
     }
 
     $paths = $this->selectPathsForWorkflow(

src/workflow/ArcanistDiffWorkflow.php

@@ -605,16 +605,8 @@ EOTEXT
     $repository_api->setBaseCommitArgumentRules(
       $this->getArgument('base', ''));
 
-    if ($repository_api->supportsRelativeLocalCommits()) {
+    if ($repository_api->supportsCommitRanges()) {
-
+      $this->parseBaseCommitArgument($this->getArgument('paths'));
-      // Parse the relative commit as soon as we can, to avoid generating
-      // caches we need to drop later and expensive discovery operations
-      // (particularly in Mercurial).
-
-      $relative = $this->getArgument('paths');
-      if ($relative) {
-        $repository_api->parseRelativeLocalCommit($relative);
-      }
     }
   }
 
@@ -821,10 +813,8 @@ EOTEXT
         }
       }
 
-    } else if ($repository_api->supportsRelativeLocalCommits()) {
-      $paths = $repository_api->getWorkingCopyStatus();
     } else {
-      throw new Exception("Unknown VCS!");
+      $paths = $repository_api->getWorkingCopyStatus();
     }
 
     foreach ($paths as $path => $mask) {
@@ -1275,9 +1265,9 @@ EOTEXT
     $this->console->writeOut("Linting...\n");
     try {
       $argv = $this->getPassthruArgumentsAsArgv('lint');
-      if ($repository_api->supportsRelativeLocalCommits()) {
+      if ($repository_api->supportsCommitRanges()) {
         $argv[] = '--rev';
-        $argv[] = $repository_api->getRelativeCommit();
+        $argv[] = $repository_api->getBaseCommit();
       }
 
       $lint_workflow = $this->buildChildWorkflow('lint', $argv);
@@ -1356,9 +1346,9 @@ EOTEXT
     $this->console->writeOut("Running unit tests...\n");
     try {
       $argv = $this->getPassthruArgumentsAsArgv('unit');
-      if ($repository_api->supportsRelativeLocalCommits()) {
+      if ($repository_api->supportsCommitRanges()) {
         $argv[] = '--rev';
-        $argv[] = $repository_api->getRelativeCommit();
+        $argv[] = $repository_api->getBaseCommit();
       }
       $unit_workflow = $this->buildChildWorkflow('unit', $argv);
       $unit_result = $unit_workflow->run();

src/workflow/ArcanistExportWorkflow.php

@@ -177,8 +177,7 @@ EOTEXT
         $parser->setRepositoryAPI($repository_api);
 
         if ($repository_api instanceof ArcanistGitAPI) {
-          $repository_api->parseRelativeLocalCommit(
+          $this->parseBaseCommitArgument($this->getArgument('paths'));
-            $this->getArgument('paths'));
           $diff = $repository_api->getFullGitDiff();
           $changes = $parser->parseDiff($diff);
           $authors = $this->getConduit()->callMethodSynchronous(
@@ -191,8 +190,7 @@ EOTEXT
             $author_dict['realName'],
             $repository_api->execxLocal('config user.email'));
         } else if ($repository_api instanceof ArcanistMercurialAPI) {
-          $repository_api->parseRelativeLocalCommit(
+          $repository_api->parseBaseCommitArgument($this->getArgument('paths'));
-            $this->getArgument('paths'));
           $diff = $repository_api->getFullMercurialDiff();
           $changes = $parser->parseDiff($diff);
           $authors = $this->getConduit()->callMethodSynchronous(

src/workflow/ArcanistLandWorkflow.php

@@ -301,7 +301,7 @@ EOTEXT
   private function findRevision() {
     $repository_api = $this->getRepositoryAPI();
 
-    $repository_api->parseRelativeLocalCommit(array($this->ontoRemoteBranch));
+    $this->parseBaseCommitArgument(array($this->ontoRemoteBranch));
 
     $revision_id = $this->getArgument('revision');
     if ($revision_id) {
@@ -484,9 +484,7 @@ EOTEXT
       }
     }
 
-    // Now that we've rebased, the merge-base of origin/master and HEAD may
+    $repository_api->reloadWorkingCopy();
-    // be different. Reparse the relative commit.
-    $repository_api->parseRelativeLocalCommit(array($this->ontoRemoteBranch));
   }
 
   private function squash() {

src/workflow/ArcanistLintWorkflow.php

@@ -240,8 +240,9 @@ EOTEXT
     if ($this->getArgument('only-new')) {
       $conduit = $this->getConduit();
       $api = $this->getRepositoryAPI();
-      $relative_commit = ($rev ? $rev : $api->resolveBaseCommit());
+      if ($rev) {
-      $api->setRelativeCommit($relative_commit);
+        $api->setBaseCommit($rev);
+      }
       $svn_root = id(new PhutilURI($api->getSourceControlPath()))->getPath();
 
       $all_paths = array();
@@ -267,7 +268,7 @@ EOTEXT
       $lint_future = $conduit->callMethod('diffusion.getlintmessages', array(
         'arcanistProject' => $this->getWorkingCopy()->getProjectID(),
         'branch' => '', // TODO: Tracking branch.
-        'commit' => $api->getRelativeCommit(),
+        'commit' => $api->getBaseCommit(),
         'files' => array_keys($all_paths),
       ));
     }

src/workflow/ArcanistPatchWorkflow.php

@@ -885,7 +885,7 @@ EOTEXT
 
     // Check to see if the bundle's base revision matches the working copy
     // base revision
-    if ($repository_api->supportsRelativeLocalCommits()) {
+    if ($repository_api->supportsLocalCommits()) {
       $bundle_base_rev = $bundle->getBaseRevision();
       if (empty($bundle_base_rev)) {
         // this means $source is SOURCE_PATCH || SOURCE_BUNDLE w/ $version < 2

src/workflow/ArcanistWhichWorkflow.php

@@ -73,20 +73,15 @@ EOTEXT
 
     $arg_commit = $this->getArgument('commit');
     if (count($arg_commit)) {
-      if (!$repository_api->supportsRelativeLocalCommits()) {
+      $this->parseBaseCommitArgument($arg_commit);
-        throw new ArcanistUsageException(
-          "This version control system does not support relative commits.");
-      } else {
-        $repository_api->parseRelativeLocalCommit($arg_commit);
-      }
     }
     $arg = $arg_commit ? ' '.head($arg_commit) : '';
 
     $repository_api->setBaseCommitArgumentRules(
       $this->getArgument('base', ''));
 
-    if ($repository_api->supportsRelativeLocalCommits()) {
+    if ($repository_api->supportsCommitRanges()) {
-      $relative = $repository_api->getRelativeCommit();
+      $relative = $repository_api->getBaseCommit();
 
       if ($this->getArgument('show-base')) {
         echo $relative."\n";