D6306: copies: write empty entries in changeset when also writing to filelog

[martinvonz (Martin von Zweigbergk)]

martinvonz created this revision.
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Herald added a reviewer: hg-reviewers.

REVISION SUMMARY
  When writing to both changeset and filelog (during transition), we
  don't want the reader to waste time by falling back to reading from
  the filelog when there is no copy metadata. Let's write out empty copy
  metadata instead (the read path is already prepared for this
  case). Thanks to Greg for pointing this out.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D6306

AFFECTED FILES
  mercurial/changelog.py
  mercurial/localrepo.py
  tests/test-copies-in-changeset.t

CHANGE DETAILS

diff --git a/tests/test-copies-in-changeset.t b/tests/test-copies-in-changeset.t
--- a/tests/test-copies-in-changeset.t
+++ b/tests/test-copies-in-changeset.t
@@ -101,6 +101,7 @@
   $ hg changesetcopies
   files: j
   p1copies: j\x00a (esc)
+  p2copies: 
   $ hg debugdata j 0
   \x01 (esc)
   copy: a
@@ -113,6 +114,14 @@
   a -> j
   $ hg showcopies --config experimental.copies.read-from=filelog-only
   a -> j
+The entries should be written to extras even if they're empty (so the client
+won't have to fall back to reading from filelogs)
+  $ echo x >> j
+  $ hg ci -m 'modify j' --config experimental.copies.write-to=compatibility
+  $ hg changesetcopies
+  files: j
+  p1copies: 
+  p2copies: 
 
 Test writing only to filelog
 
diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
--- a/mercurial/localrepo.py
+++ b/mercurial/localrepo.py
@@ -2557,7 +2557,13 @@
         writecopiesto = self.ui.config('experimental', 'copies.write-to')
         writefilecopymeta = writecopiesto != 'changeset-only'
         p1copies, p2copies = None, None
-        if writecopiesto in ('changeset-only', 'compatibility'):
+        # If writing only to changeset extras, use None to indicate that
+        # no entry should be written. If writing to both, write an empty
+        # entry to prevent the reader from falling back to reading filelogs.
+        if writecopiesto == 'changeset-only':
+            p1copies = ctx.p1copies() or None
+            p2copies = ctx.p2copies() or None
+        elif writecopiesto == 'compatibility':
             p1copies = ctx.p1copies()
             p2copies = ctx.p2copies()
         with self.lock(), self.transaction("commit") as tr:
diff --git a/mercurial/changelog.py b/mercurial/changelog.py
--- a/mercurial/changelog.py
+++ b/mercurial/changelog.py
@@ -591,11 +591,11 @@
             elif branch in (".", "null", "tip"):
                 raise error.StorageError(_('the name \'%s\' is reserved')
                                          % branch)
-        if (p1copies or p2copies) and extra is None:
+        if (p1copies is not None or p2copies is not None) and extra is None:
             extra = {}
-        if p1copies:
+        if p1copies is not None:
             extra['p1copies'] = encodecopies(p1copies)
-        if p2copies:
+        if p2copies is not None:
             extra['p2copies'] = encodecopies(p2copies)
 
         if extra:



To: martinvonz, #hg-reviewers
Cc: mercurial-devel