When saving and restoring local state in Mercurial, also save and restore bookmarks

Summary:
Ref PHI1808. In Mercurial, we must save and restore bookmark state explicitly.

  - Save and restore bookmarks.
  - Clean up concepts in "arc-ls-markers" slightly, so we don't need separate "isCurrent" and "isActive" flags, hopefully.

I believe the totality of Mercurial state is:

  - A (non-bare) working copy points at exactly one commit (which might be the empty/null commit, in an empty repository).
  - A working copy has exactly one active branch.
    - Each branch has zero or more heads.
    - Each head may be closed.
    - Each (non-null) commit belongs to exactly one branch.
    - Note that the active branch may have zero heads and zero commits which belong to it!
  - A working copy has zero or one active bookmark.

To capture this, we now emit:

  - A list of branch heads. If a branch head is a working copy commit, that head is flagged as active.
  - A list of bookmarks. If a bookmark is the current bookmark, that bookmark is flagged as active.
  - A single "branch-state" virtual marker. This covers the case where you have run "hg branch X" to create X, but no objects in the working copy actually correspond to X yet. It also covers the case where you are on a concrete branch, but not any head of that branch.
  - A single "commit-state" virtual marker. This always shows the current commit in the working copy.

Test Plan:
  - Useful states to test are:
    - Empty repository (not all commands currently work here).
    - Normal repository, on a bookmark.
    - Normal repository, no bookmark.
    - "hg up 123" to update to somewhere in history.
    - "hg branch X", to start a new branch with no commits.
  - Ran "arc branches" and "arc bookmarks" in various states. Saw generally sensible output.
  - Ran "arc land --hold ..." in various states against a failing remote. Saw generally sensible output, and saw working properly restored to the original state.

Differential Revision: https://secure.phabricator.com/D21396

src/repository/marker/ArcanistMarkerRef.php

@@ -9,6 +9,8 @@ final class ArcanistMarkerRef
 
   const TYPE_BRANCH = 'branch';
   const TYPE_BOOKMARK = 'bookmark';
+  const TYPE_COMMIT_STATE = 'commit-state';
+  const TYPE_BRANCH_STATE = 'branch-state';
 
   private $name;
   private $markerType;
@@ -148,6 +150,14 @@ final class ArcanistMarkerRef
     return ($this->getMarkerType() === self::TYPE_BRANCH);
   }
 
+  public function isCommitState() {
+    return ($this->getMarkerType() === self::TYPE_COMMIT_STATE);
+  }
+
+  public function isBranchState() {
+    return ($this->getMarkerType() === self::TYPE_BRANCH_STATE);
+  }
+
   public function attachCommitRef(ArcanistCommitRef $ref) {
     return $this->attachHardpoint(self::HARDPOINT_COMMITREF, $ref);
   }

src/repository/marker/ArcanistMercurialRepositoryMarkerQuery.php

@@ -71,10 +71,6 @@ final class ArcanistMercurialRepositoryMarkerQuery
       }
 
       $node = $item['node'];
-      if (!$node) {
-        // NOTE: For now, we ignore the virtual "current branch" marker.
-        continue;
-      }
 
       switch ($item['type']) {
         case 'branch':
@@ -83,8 +79,11 @@ final class ArcanistMercurialRepositoryMarkerQuery
         case 'bookmark':
           $marker_type = ArcanistMarkerRef::TYPE_BOOKMARK;
           break;
-        case 'commit':
-          $marker_type = null;
+        case 'commit-state':
+          $marker_type = ArcanistMarkerRef::TYPE_COMMIT_STATE;
+          break;
+        case 'branch-state':
+          $marker_type = ArcanistMarkerRef::TYPE_BRANCH_STATE;
           break;
         default:
           throw new Exception(
@@ -94,11 +93,6 @@ final class ArcanistMercurialRepositoryMarkerQuery
               $item['type']));
       }
 
-      if ($marker_type === null) {
-        // NOTE: For now, we ignore the virtual "head" marker.
-        continue;
-      }
-
       $commit_ref = $api->newCommitRef()
         ->setCommitHash($node);
 

src/repository/state/ArcanistMercurialLocalState.php

@@ -5,40 +5,105 @@ final class ArcanistMercurialLocalState
 
   private $localCommit;
   private $localBranch;
+  private $localBookmark;
 
   protected function executeSaveLocalState() {
     $api = $this->getRepositoryAPI();
     $log = $this->getWorkflow()->getLogEngine();
 
-    // TODO: Both of these can be pulled from "hg arc-ls-markers" more
-    // efficiently.
+    $markers = $api->newMarkerRefQuery()
+      ->execute();
 
-    $this->localCommit = $api->getCanonicalRevisionName('.');
+    $local_commit = null;
+    foreach ($markers as $marker) {
+      if ($marker->isCommitState()) {
+        $local_commit = $marker->getCommitHash();
+      }
+    }
 
-    list($branch) = $api->execxLocal('branch');
-    $this->localBranch = trim($branch);
-
-    $log->writeTrace(
-      pht('SAVE STATE'),
+    if ($local_commit === null) {
+      throw new Exception(
         pht(
+          'Unable to identify the current commit in the working copy.'));
+    }
+
+    $this->localCommit = $local_commit;
+
+    $local_branch = null;
+    foreach ($markers as $marker) {
+      if ($marker->isBranchState()) {
+        $local_branch = $marker->getName();
+        break;
+      }
+    }
+
+    if ($local_branch === null) {
+      throw new Exception(
+        pht(
+          'Unable to identify the current branch in the working copy.'));
+    }
+
+    if ($local_branch !== null) {
+      $this->localBranch = $local_branch;
+    }
+
+    $local_bookmark = null;
+    foreach ($markers as $marker) {
+      if ($marker->isBookmark()) {
+        if ($marker->getIsActive()) {
+          $local_bookmark = $marker->getName();
+          break;
+        }
+      }
+    }
+
+    if ($local_bookmark !== null) {
+      $this->localBookmark = $local_bookmark;
+    }
+
+    $has_bookmark = ($this->localBookmark !== null);
+
+    if ($has_bookmark) {
+      $location = pht(
+        'Saving local state (at "%s" on branch "%s", bookmarked as "%s").',
+        $api->getDisplayHash($this->localCommit),
+        $this->localBranch,
+        $this->localBookmark);
+    } else {
+      $location = pht(
         'Saving local state (at "%s" on branch "%s").',
         $api->getDisplayHash($this->localCommit),
-        $this->localBranch));
+        $this->localBranch);
+    }
+
+    $log->writeTrace(pht('SAVE STATE'), $location);
   }
 
   protected function executeRestoreLocalState() {
     $api = $this->getRepositoryAPI();
     $log = $this->getWorkflow()->getLogEngine();
 
-    $log->writeStatus(
-      pht('LOAD STATE'),
-      pht(
+    if ($this->localBookmark !== null) {
+      $location = pht(
+        'Restoring local state (at "%s" on branch "%s", bookmarked as "%s").',
+        $api->getDisplayHash($this->localCommit),
+        $this->localBranch,
+        $this->localBookmark);
+    } else {
+      $location = pht(
         'Restoring local state (at "%s" on branch "%s").',
         $api->getDisplayHash($this->localCommit),
-        $this->localBranch));
+        $this->localBranch);
+    }
+
+    $log->writeStatus(pht('LOAD STATE'), $location);
 
     $api->execxLocal('update -- %s', $this->localCommit);
     $api->execxLocal('branch --force -- %s', $this->localBranch);
+
+    if ($this->localBookmark !== null) {
+      $api->execxLocal('bookmark --force -- %s', $this->localBookmark);
+    }
   }
 
   protected function executeDiscardLocalState() {
@@ -70,6 +135,12 @@ final class ArcanistMercurialLocalState
       'hg branch --force -- %s',
       $this->localBranch);
 
+    if ($this->localBookmark !== null) {
+      $commands[] = csprintf(
+        'hg bookmark --force -- %s',
+        $this->localBookmark);
+    }
+
     return $commands;
   }
 

support/hg/arc-hg.py

@@ -85,21 +85,17 @@ def localmarkers(ui, repo):
   active_node = repo[b'.'].node()
   all_heads = set(repo.heads())
   current_name = repo.dirstate.branch()
-  saw_current = False
-  saw_active = False
 
   branch_list = repo.branchmap().iterbranches()
   for branch_name, branch_heads, tip_node, is_closed in branch_list:
     for head_node in branch_heads:
-      is_active = (head_node == active_node)
+
+      is_active = False
+      if branch_name == current_name:
+        if head_node == active_node:
+          is_active = True
+
       is_tip = (head_node == tip_node)
-      is_current = (branch_name == current_name)
-
-      if is_current:
-        saw_current = True
-
-      if is_active:
-        saw_active = True
 
       if is_closed:
         head_closed = True
@@ -115,26 +111,9 @@ def localmarkers(ui, repo):
         'isActive': is_active,
         'isClosed': head_closed,
         'isTip': is_tip,
-        'isCurrent': is_current,
         'description': description,
       })
 
-  # If the current branch (selected with "hg branch X") is not reflected in
-  # the list of heads we selected, add a virtual head for it so callers get
-  # a complete picture of repository marker state.
-
-  if not saw_current:
-    markers.append({
-      'type': 'branch',
-      'name': current_name,
-      'node': None,
-      'isActive': False,
-      'isClosed': False,
-      'isTip': False,
-      'isCurrent': True,
-      'description': None,
-    })
-
   bookmarks = repo._bookmarks
   active_bookmark = repo._activebookmark
 
@@ -142,9 +121,6 @@ def localmarkers(ui, repo):
     is_active = (active_bookmark == bookmark_name)
     description = repo[bookmark_node].description()
 
-    if is_active:
-      saw_active = True
-
     markers.append({
       'type': 'bookmark',
       'name': bookmark_name,
@@ -153,19 +129,34 @@ def localmarkers(ui, repo):
       'description': description,
     })
 
-  # If the current working copy state is not the head of a branch and there is
-  # also no active bookmark, add a virtual marker for it so callers can figure
-  # out exactly where we are.
+  # Add virtual markers for the current commit state and current branch state
+  # so callers can figure out exactly where we are.
+
+  # Common cases where this matters include:
+
+  # You run "hg update 123" to update to an older revision. Your working
+  # copy commit will not be a branch head or a bookmark.
+
+  # You run "hg branch X" to create a new branch, but have not made any commits
+  # yet. Your working copy branch will not be reflected in any commits.
 
-  if not saw_active:
   markers.append({
-      'type': 'commit',
-      'name': None,
-      'node': node.hex(active_node),
-      'isActive': False,
+    'type': 'branch-state',
+    'name': current_name,
+    'node': None,
+    'isActive': True,
+    'isClosed': False,
+    'isTip': False,
+    'description': None,
+  })
+
+  markers.append({
+    'type': 'commit-state',
+    'name': None,
+    'node': node.hex(active_node),
+    'isActive': True,
     'isClosed': False,
     'isTip': False,
-      'isCurrent': True,
     'description': repo[b'.'].description(),
   })