revlogv2: track pending write in the docket and expose it to hooks

The docket is now able to write pending data. We could have used a distinct
intermediate files, however keeping everything in the same file will make it
simpler to keep track of the various involved files if necessary.

However it might prove more complicated for streaming clone. This will be dealt
with later.

Note that we lifted the stderr redirection in the test since we no longer suffer
from "unkown working directory parent" message.

Differential Revision: https://phab.mercurial-scm.org/D10631

mercurial/changelog.py

@@ -395,7 +395,6 b' class changelog(revlog.revlog):'
         ``concurrencychecker`` will be passed to the revlog init function, see
         the documentation there.
         """
-
         revlog.revlog.__init__(
             self,
             opener,
@@ -484,6 +483,8 b' class changelog(revlog.revlog):'
     def _writepending(self, tr):
         """create a file containing the unfinalized state for
         pretxnchangegroup"""
+        if self._docket:
+            return self._docket.write(tr, pending=True)
         if self._delaybuf:
             # make a temporary copy of the index
             fp1 = self._realopener(self._indexfile)

mercurial/configitems.py

@@ -1150,7 +1150,6 b' coreconfigitem('
 )
 # "out of experimental" todo list.
 #
-# * expose transaction content hooks during pre-commit validation
 # * include management of a persistent nodemap in the main docket
 # * enforce a "no-truncate" policy for mmap safety
 #      - for censoring operation

mercurial/revlog.py

@@ -529,7 +529,9 b' class revlog(object):'
             if self._initempty:
                 self._docket = docketutil.default_docket(self, header)
             else:
-                self._docket = docketutil.parse_docket(self, entry_data)
+                self._docket = docketutil.parse_docket(
+                    self, entry_data, use_pending=self._trypending
+                )
             self._indexfile = self._docket.index_filepath()
             index_data = b''
             index_size = self._docket.index_end

mercurial/revlogutils/docket.py

@@ -19,6 +19,10 b' from __future__ import absolute_import'
 
 import struct
 
+from .. import (
+    error,
+)
+
 from . import (
     constants,
 )
@@ -29,19 +33,35 b' from . import ('
 #          |   This is mandatory as docket must be compatible with the previous
 #          |   revlog index header.
 # * 8 bytes: size of index data
-S_HEADER = struct.Struct(constants.INDEX_HEADER.format + 'L')
+# * 8 bytes: pending size of index data
+S_HEADER = struct.Struct(constants.INDEX_HEADER.format + 'LL')
 
 
 class RevlogDocket(object):
     """metadata associated with revlog"""
 
-    def __init__(self, revlog, version_header=None, index_end=0):
+    def __init__(
+        self,
+        revlog,
+        use_pending=False,
+        version_header=None,
+        index_end=0,
+        pending_index_end=0,
+    ):
         self._version_header = version_header
+        self._read_only = bool(use_pending)
         self._dirty = False
         self._radix = revlog.radix
         self._path = revlog._docket_file
         self._opener = revlog.opener
-        self._index_end = index_end
+        # this assert should be True as long as we have a single index filename
+        assert index_end <= pending_index_end
+        self._initial_index_end = index_end
+        self._pending_index_end = pending_index_end
+        if use_pending:
+            self._index_end = self._pending_index_end
+        else:
+            self._index_end = self._initial_index_end
 
     def index_filepath(self):
         """file path to the current index file associated to this docket"""
@@ -58,22 +78,38 b' class RevlogDocket(object):'
             self._index_end = new_size
             self._dirty = True
 
-    def write(self, transaction, stripping=False):
+    def write(self, transaction, pending=False, stripping=False):
         """write the modification of disk if any
 
         This make the new content visible to all process"""
-        if self._dirty:
+        if not self._dirty:
+            return False
+        else:
+            if self._read_only:
+                msg = b'writing read-only docket: %s'
+                msg %= self._path
+                raise error.ProgrammingError(msg)
             if not stripping:
                 # XXX we could, leverage the docket while stripping. However it
                 # is not powerfull enough at the time of this comment
                 transaction.addbackup(self._path, location=b'store')
             with self._opener(self._path, mode=b'w', atomictemp=True) as f:
-                f.write(self._serialize())
-            self._dirty = False
+                f.write(self._serialize(pending=pending))
+            # if pending we still need to the write final data eventually
+            self._dirty = pending
+            return True
 
-    def _serialize(self):
+    def _serialize(self, pending=False):
+        if pending:
+            official_index_end = self._initial_index_end
+        else:
+            official_index_end = self._index_end
+
+        # this assert should be True as long as we have a single index filename
+        assert official_index_end <= self._index_end
         data = (
             self._version_header,
+            official_index_end,
             self._index_end,
         )
         return S_HEADER.pack(*data)
@@ -88,13 +124,15 b' def default_docket(revlog, version_heade'
     return docket
 
 
-def parse_docket(revlog, data):
+def parse_docket(revlog, data, use_pending=False):
     """given some docket data return a docket object for the given revlog"""
     header = S_HEADER.unpack(data[: S_HEADER.size])
-    version_header, index_size = header
+    version_header, index_size, pending_index_size = header
     docket = RevlogDocket(
         revlog,
+        use_pending=use_pending,
         version_header=version_header,
         index_end=index_size,
+        pending_index_end=pending_index_size,
     )
     return docket

tests/test-transaction-safety.t

@@ -46,13 +46,13 b' synchronisation+output script:'
   $ cat << EOF > script/external.sh
   > #!/bin/sh
   > $RUNTESTDIR/testlib/wait-on-file 5 $HG_TEST_FILE_EXT_UNLOCK $HG_TEST_FILE_EXT_WAITING
-  > hg log --rev 'tip' -T 'external: {rev} {desc}\n' > $TESTTMP/output/external.out 2>/dev/null
+  > hg log --rev 'tip' -T 'external: {rev} {desc}\n' > $TESTTMP/output/external.out
   > touch $HG_TEST_FILE_EXT_DONE
   > EOF
   $ chmod +x script/external.sh
   $ cat << EOF > script/internal.sh
   > #!/bin/sh
-  > hg log --rev 'tip' -T 'internal: {rev} {desc}\n' > $TESTTMP/output/internal.out 2>/dev/null
+  > hg log --rev 'tip' -T 'internal: {rev} {desc}\n' > $TESTTMP/output/internal.out
   > $RUNTESTDIR/testlib/wait-on-file 5 $HG_TEST_FILE_EXT_DONE $HG_TEST_FILE_EXT_UNLOCK
   > EOF
   $ chmod +x script/internal.sh
@@ -124,8 +124,7 b' the repository should still be inline (f'
   $ make_one_commit first
   pre-commit: -1 
   external: -1 
-  internal: 0 first (revlogv1 !)
-  internal: -1  (revlogv2 known-bad-output !)
+  internal: 0 first
   post-tr:  0 first
 
 #if revlogv1
@@ -150,8 +149,7 b' the repository should still be inline (f'
   $ make_one_commit second
   pre-commit: 0 first
   external: 0 first
-  internal: 1 second (revlogv1 !)
-  internal: 0 first (revlogv2 known-bad-output !)
+  internal: 1 second
   post-tr:  1 second
 
 #if revlogv1
@@ -177,8 +175,7 b' the repository should still be inline (f'
   pre-commit: 1 second
   warning: repository is unrelated
   external: 1 second
-  internal: 5 r3 (revlogv1 !)
-  internal: 1 second (revlogv2 known-bad-output !)
+  internal: 5 r3
   post-tr:  5 r3
 
 #if revlogv1
@@ -203,8 +200,7 b' the repository should no longer be inlin'
   $ make_one_pull 400
   pre-commit: 5 r3
   external: 5 r3
-  internal: 402 r400 (revlogv1 !)
-  internal: 5 r3 (revlogv2 known-bad-output !)
+  internal: 402 r400
   post-tr:  402 r400
 
 #if revlogv1
@@ -229,8 +225,7 b' the repository should no longer be inlin'
   $ make_one_commit third
   pre-commit: 402 r400
   external: 402 r400
-  internal: 403 third (revlogv1 !)
-  internal: 402 r400 (revlogv2 known-bad-output !)
+  internal: 403 third
   post-tr:  403 third
 
 #if revlogv1
@@ -256,8 +251,7 b' the repository should no longer be inlin'
   $ make_one_pull tip
   pre-commit: 403 third
   external: 403 third
-  internal: 503 r500 (revlogv1 !)
-  internal: 403 third (revlogv2 known-bad-output !)
+  internal: 503 r500
   post-tr:  503 r500
 
 #if revlogv1