changeset 48701:f8f2ecdde4b5

branchmap: skip obsolete revisions while computing heads

It's time to make this part of core Mercurial obsolescence-aware.

Not considering obsolete revisions when computing heads is clearly what
Mercurial should do. But there are a couple of small issues:

- Let's say tip of the repo is obsolete. There are two ways of finding tiprev
  for branchcache (both are in use): looking at input data for update() and
  looking at computed heads after update(). Previously, repo tip would be
  tiprev of the branchcache. With this patch, an obsolete revision can no
  longer be tiprev. And depending on what way we use for finding tiprev (input
  data vs computed heads) we'll get a different result. This is relevant when
  recomputing cache key from cache contents, and may lead to updating cache for
  obsolete revisions multiple times (not from scratch, because it still would
  be considered valid for a subset of revisions in the repo).

- If all commits on a branch are obsolete, the branchcache will include that
  branch, but the list of heads will be empty (that's why there's now `if not
  heads` when recomputing tiprev/tipnode from cache contents). Having an entry
  for every branch is currently required for notify extension (and
  test-notify.t to pass), because notify doesn't handle revsets in its
  subscription config very well and will throw an error if e.g. a branch
  doesn't exist.

- Cloning static HTTP repos may try to stat() a non-existent obsstore file. The
  issue is that we now care about obsolescence during clone, but statichttpvfs
  doesn't implement a stat method, so a regular vfs.stat() is used, and it
  assumes that file is local and calls os.stat().  During a clone, we're trying
  to stat() .hg/store/obsstore, but in static HTTP case we provide a literal
  URL to the obsstore file on the remote as if it were a local file path. On
  windows it actually results in a failure in test-static-http.t.

The first issue is going to be addressed in a series dedicated to making sure
branchcache is properly and timely written on disk (it wasn't perfect even
before this patch, but there aren't enough tests to demonstrate that). The
second issue will be addressed in a future patch for notify extension that will
make it not raise an exception if a branch doesn't exist. And the third one was
partially addressed in the previous patch in this series and will be properly
fixed in a future patch when this series is accepted.

filteredhash() grows a keyword argument to make sure that branchcache is also
invalidated when there are new obsolete revisions in its repo view. This way
the on-disk cache format is unchanged and compatible between versions (although
it will obviously be recomputed when switching versions before/after this patch
and the repo has obsolete revisions).

There's one test that uses plain `hg up` without arguments while updated to a
pruned commit. To make this test pass, simply return current working directory
parent. Later in this series this code will be replaced by what prune command
does: updating to the closest non-obsolete ancestor.

Test changes:

test-branch-change.t: update branch head and cache update message. The head of
default listed in hg heads is changed because revision 2 was rewritten as 7,
and 1 is the closest ancestor on the same branch, so it's the head of default
now.

The cache invalidation message appears now because of the cache hash change,
since we're now accounting for obsolete revisions. Here's some context:

"served.hidden" repo filter means everything is visible (no filtered
revisions), so before this series branch2-served.hidden file would not contain
any cache hash, only revnum and node. Now it also has a hash when there are
obsolete changesets in the repo. The command that the message appears for is
changing branch of 5 and 6, which are now obsolete, so the cache hash changes.

In general, when cache is simply out-of-date, it can be updated using the old
version as a base. But if cache hash differs, then the cache for that
particular repo filter is recomputed (at least with the current
implementation). This is what happens here.

test-obsmarker-template.t: the pull reports 2 heads changed, but after that the
repo correctly sees only 1. The new message could be better, but it's still an
improvement over the previous one where hg pull suggested merging with an
obsolete revision.

test-obsolete.t: we can see these revisions in hg log --hidden, but they
shouldn't be considered heads even with --hidden.

test-rebase-obsolete{,2}.t: there were new heads created previously after
making new orphan changesets, but they weren't detected. Now we are properly
detecting and reporting them.

test-rebase-obsolete4.t: there's only one head now because the other head is
pruned and was falsely reported before.

test-static-http.t: add obsstore to the list of requested files. This file
doesn't exist on the remotes, but clients want it anyway (they get 404). This
is fine, because there are other nonexistent files that clients request, like
.hg/bookmarks or .hg/cache/tags2-served.

Differential Revision: https://phab.mercurial-scm.org/D12097

--- a/mercurial/branchmap.py	Fri Jan 28 19:07:52 2022 +0300
+++ b/mercurial/branchmap.py	Fri Jan 07 11:53:23 2022 +0300
@@ -17,6 +17,7 @@
 from . import (
     encoding,
     error,
+    obsolete,
     pycompat,
     scmutil,
     util,
@@ -184,7 +185,7 @@
 
     The first line is used to check if the cache is still valid. If the
     branch cache is for a filtered repo view, an optional third hash is
-    included that hashes the hashes of all filtered revisions.
+    included that hashes the hashes of all filtered and obsolete revisions.
 
     The open/closed state is represented by a single letter 'o' or 'c'.
     This field can be used to avoid changelog reads when determining if a
@@ -357,7 +358,8 @@
         - True when cache is up to date or a subset of current repo."""
         try:
             return (self.tipnode == repo.changelog.node(self.tiprev)) and (
-                self.filteredhash == scmutil.filteredhash(repo, self.tiprev)
+                self.filteredhash
+                == scmutil.filteredhash(repo, self.tiprev, needobsolete=True)
             )
         except IndexError:
             return False
@@ -478,6 +480,9 @@
         # use the faster unfiltered parent accessor.
         parentrevs = repo.unfiltered().changelog.parentrevs
 
+        # Faster than using ctx.obsolete()
+        obsrevs = obsolete.getrevs(repo, b'obsolete')
+
         for branch, newheadrevs in pycompat.iteritems(newbranches):
             # For every branch, compute the new branchheads.
             # A branchhead is a revision such that no descendant is on
@@ -518,6 +523,11 @@
             bheadset = {cl.rev(node) for node in bheads}
             uncertain = set()
             for newrev in sorted(newheadrevs):
+                if newrev in obsrevs:
+                    # We ignore obsolete changesets as they shouldn't be
+                    # considered heads.
+                    continue
+
                 if not bheadset:
                     bheadset.add(newrev)
                     continue
@@ -525,13 +535,22 @@
                 parents = [p for p in parentrevs(newrev) if p != nullrev]
                 samebranch = set()
                 otherbranch = set()
+                obsparents = set()
                 for p in parents:
-                    if p in bheadset or getbranchinfo(p)[0] == branch:
+                    if p in obsrevs:
+                        # We ignored this obsolete changeset earlier, but now
+                        # that it has non-ignored children, we need to make
+                        # sure their ancestors are not considered heads. To
+                        # achieve that, we will simply treat this obsolete
+                        # changeset as a parent from other branch.
+                        obsparents.add(p)
+                    elif p in bheadset or getbranchinfo(p)[0] == branch:
                         samebranch.add(p)
                     else:
                         otherbranch.add(p)
-                if otherbranch and not (len(bheadset) == len(samebranch) == 1):
+                if not (len(bheadset) == len(samebranch) == 1):
                     uncertain.update(otherbranch)
+                    uncertain.update(obsparents)
                 bheadset.difference_update(samebranch)
                 bheadset.add(newrev)
 
@@ -540,11 +559,12 @@
                     topoheads = set(cl.headrevs())
                 if bheadset - topoheads:
                     floorrev = min(bheadset)
-                    ancestors = set(cl.ancestors(newheadrevs, floorrev))
-                    bheadset -= ancestors
+                    if floorrev <= max(uncertain):
+                        ancestors = set(cl.ancestors(uncertain, floorrev))
+                        bheadset -= ancestors
             bheadrevs = sorted(bheadset)
             self[branch] = [cl.node(rev) for rev in bheadrevs]
-            tiprev = bheadrevs[-1]
+            tiprev = max(newheadrevs)
             if tiprev > ntiprev:
                 ntiprev = tiprev
 
@@ -553,15 +573,24 @@
             self.tipnode = cl.node(ntiprev)
 
         if not self.validfor(repo):
-            # cache key are not valid anymore
+            # old cache key is now invalid for the repo, but we've just updated
+            # the cache and we assume it's valid, so let's make the cache key
+            # valid as well by recomputing it from the cached data
             self.tipnode = repo.nullid
             self.tiprev = nullrev
             for heads in self.iterheads():
+                if not heads:
+                    # all revisions on a branch are obsolete
+                    continue
+                # note: tiprev is not necessarily the tip revision of repo,
+                # because the tip could be obsolete (i.e. not a head)
                 tiprev = max(cl.rev(node) for node in heads)
                 if tiprev > self.tiprev:
                     self.tipnode = cl.node(tiprev)
                     self.tiprev = tiprev
-        self.filteredhash = scmutil.filteredhash(repo, self.tiprev)
+        self.filteredhash = scmutil.filteredhash(
+            repo, self.tiprev, needobsolete=True
+        )
 
         duration = util.timer() - starttime
         repo.ui.log(

--- a/mercurial/destutil.py	Fri Jan 28 19:07:52 2022 +0300
+++ b/mercurial/destutil.py	Fri Jan 07 11:53:23 2022 +0300
@@ -79,6 +79,9 @@
             node = repo.revs(b'max(%ln)', successors).first()
             if bookmarks.isactivewdirparent(repo):
                 movemark = repo[b'.'].node()
+        else:
+            # TODO: copy hg prune logic
+            node = repo[b'.'].node()
     return node, movemark, None
 
 

--- a/mercurial/scmutil.py	Fri Jan 28 19:07:52 2022 +0300
+++ b/mercurial/scmutil.py	Fri Jan 07 11:53:23 2022 +0300
@@ -349,7 +349,7 @@
         self._newfiles.add(f)
 
 
-def filteredhash(repo, maxrev):
+def filteredhash(repo, maxrev, needobsolete=False):
     """build hash of filtered revisions in the current repoview.
 
     Multiple caches perform up-to-date validation by checking that the
@@ -358,22 +358,33 @@
     of revisions in the view may change without the repository tiprev and
     tipnode changing.
 
-    This function hashes all the revs filtered from the view and returns
-    that SHA-1 digest.
+    This function hashes all the revs filtered from the view (and, optionally,
+    all obsolete revs) up to maxrev and returns that SHA-1 digest.
     """
     cl = repo.changelog
-    if not cl.filteredrevs:
-        return None
-    key = cl._filteredrevs_hashcache.get(maxrev)
-    if not key:
-        revs = sorted(r for r in cl.filteredrevs if r <= maxrev)
+    if needobsolete:
+        obsrevs = obsolete.getrevs(repo, b'obsolete')
+        if not cl.filteredrevs and not obsrevs:
+            return None
+        # TODO: obsrevs should be a frozenset, but right now obsolete.getrevs()
+        # may return a set, which is not a hashable type.
+        key = (maxrev, hash(cl.filteredrevs), hash(frozenset(obsrevs)))
+    else:
+        if not cl.filteredrevs:
+            return None
+        key = maxrev
+        obsrevs = frozenset()
+
+    result = cl._filteredrevs_hashcache.get(key)
+    if not result:
+        revs = sorted(r for r in cl.filteredrevs | obsrevs if r <= maxrev)
         if revs:
             s = hashutil.sha1()
             for rev in revs:
                 s.update(b'%d;' % rev)
-            key = s.digest()
-            cl._filteredrevs_hashcache[maxrev] = key
-    return key
+            result = s.digest()
+            cl._filteredrevs_hashcache[key] = result
+    return result
 
 
 def walkrepos(path, followsym=False, seen_dirs=None, recurse=False):

--- a/tests/test-branch-change.t	Fri Jan 28 19:07:52 2022 +0300
+++ b/tests/test-branch-change.t	Fri Jan 07 11:53:23 2022 +0300
@@ -185,6 +185,7 @@
   changed branch on 2 changesets
   updating the branch cache
   invalid branch cache (served): tip differs
+  invalid branch cache (served.hidden): tip differs
 
   $ hg glog -r '(.^)::'
   @  9:de1404b45a69 Added e
@@ -211,7 +212,7 @@
   secret                        11:38a9b2d53f98
   foo                            7:8a4729a5e2b8
   wat                            9:de1404b45a69 (inactive)
-  default                        2:28ad74487de9 (inactive)
+  default                        1:29becc82797a (inactive)
   $ hg branch
   secret
 

--- a/tests/test-obsmarker-template.t	Fri Jan 28 19:07:52 2022 +0300
+++ b/tests/test-obsmarker-template.t	Fri Jan 07 11:53:23 2022 +0300
@@ -1762,7 +1762,7 @@
   2 new obsolescence markers
   obsoleted 1 changesets
   new changesets 7a230b46bf61 (1 drafts)
-  (run 'hg heads' to see heads, 'hg merge' to merge)
+  (run 'hg heads' to see heads)
   $ hg log --hidden -G
   o  changeset:   2:7a230b46bf61
   |  tag:         tip

--- a/tests/test-obsolete.t	Fri Jan 28 19:07:52 2022 +0300
+++ b/tests/test-obsolete.t	Fri Jan 07 11:53:23 2022 +0300
@@ -169,10 +169,6 @@
   5:5601fb93a350 (draft) [tip ] add new_3_c
   $ hg heads --hidden
   5:5601fb93a350 (draft) [tip ] add new_3_c
-  4:ca819180edb9 (draft *obsolete*) [ ] add new_2_c [rewritten as 5:5601fb93a350]
-  3:cdbce2fbb163 (draft *obsolete*) [ ] add new_c [rewritten as 4:ca819180edb9]
-  2:245bde4270cd (draft *obsolete*) [ ] add original_c [rewritten as 3:cdbce2fbb163]
-
 
 check that summary does not report them
 
@@ -193,7 +189,7 @@
    add new_3_c
   branch: default
   commit: (clean)
-  update: 3 new changesets, 4 branch heads (merge)
+  update: (current)
   phases: 6 draft
   remote: 3 outgoing
 

--- a/tests/test-rebase-obsolete.t	Fri Jan 28 19:07:52 2022 +0300
+++ b/tests/test-rebase-obsolete.t	Fri Jan 07 11:53:23 2022 +0300
@@ -650,6 +650,7 @@
   $ hg add J
   $ hg commit -m J
   1 new orphan changesets
+  created new head
   $ hg debugobsolete `hg log --rev . -T '{node}'`
   1 new obsolescence markers
   obsoleted 1 changesets

--- a/tests/test-rebase-obsolete2.t	Fri Jan 28 19:07:52 2022 +0300
+++ b/tests/test-rebase-obsolete2.t	Fri Jan 07 11:53:23 2022 +0300
@@ -47,6 +47,7 @@
   $ hg add C
   $ hg commit -m C
   1 new orphan changesets
+  created new head
   $ hg log -G
   @  4:212cb178bcbb C
   |
@@ -73,6 +74,7 @@
   $ hg add D
   $ hg commit -m D
   1 new orphan changesets
+  created new head
   $ hg --hidden strip -r 'desc(B1)'
   saved backup bundle to $TESTTMP/obsskip/.hg/strip-backup/86f6414ccda7-b1c452ee-backup.hg
   1 new orphan changesets
@@ -194,6 +196,7 @@
   $ hg add foo
   $ hg commit -m "bar foo"
   1 new orphan changesets
+  created new head
   $ hg log -G
   @  14:73568ab6879d bar foo
   |

--- a/tests/test-rebase-obsolete4.t	Fri Jan 28 19:07:52 2022 +0300
+++ b/tests/test-rebase-obsolete4.t	Fri Jan 07 11:53:23 2022 +0300
@@ -169,7 +169,7 @@
    D
   branch: default
   commit: 1 modified, 1 added, 1 unknown, 1 unresolved
-  update: 1 new changesets, 2 branch heads (merge)
+  update: (current)
   phases: 3 draft
   rebase: 0 rebased, 2 remaining (rebase --continue)
 

--- a/tests/test-static-http.t	Fri Jan 28 19:07:52 2022 +0300
+++ b/tests/test-static-http.t	Fri Jan 07 11:53:23 2022 +0300
@@ -256,6 +256,7 @@
   /remote-with-names/.hg/store/data/%7E2ehgtags.i (no-py37 !)
   /remote-with-names/.hg/store/data/foo.i
   /remote-with-names/.hg/store/data/~2ehgtags.i (py37 !)
+  /remote-with-names/.hg/store/obsstore
   /remote-with-names/.hg/store/requires
   /remote/.hg/bookmarks
   /remote/.hg/bookmarks.current
@@ -276,6 +277,7 @@
   /remote/.hg/store/data/quux.i
   /remote/.hg/store/data/~2edotfile%20with%20spaces.i (py37 !)
   /remote/.hg/store/data/~2ehgtags.i (py37 !)
+  /remote/.hg/store/obsstore
   /remote/.hg/store/requires
   /remotempty/.hg/bookmarks
   /remotempty/.hg/bookmarks.current