revlog: add a function to build index entry tuple

Keeping index entry as tuple make sense for performance reason, however it does
not means we need to manually build that tuple for all piece of python code that
are not performance critical.

So we add a nice function responsible to build the tuple using argument using
explicit keyword argument.

Differential Revision: https://phab.mercurial-scm.org/D10793

mercurial/revlogutils/__init__.py

@@ -9,8 +9,50 b' from __future__ import absolute_import'
 
 from ..interfaces import repository
 
+# See mercurial.revlogutils.constants for doc
+COMP_MODE_INLINE = 2
+
 
 def offset_type(offset, type):
     if (type & ~repository.REVISION_FLAGS_KNOWN) != 0:
         raise ValueError(b'unknown revlog index flags: %d' % type)
     return int(int(offset) << 16 | type)
+
+
+def entry(
+    data_offset,
+    data_compressed_length,
+    data_delta_base,
+    link_rev,
+    parent_rev_1,
+    parent_rev_2,
+    node_id,
+    flags=0,
+    data_uncompressed_length=-1,
+    data_compression_mode=COMP_MODE_INLINE,
+    sidedata_offset=0,
+    sidedata_compressed_length=0,
+    sidedata_compression_mode=COMP_MODE_INLINE,
+):
+    """Build one entry from symbolic name
+
+    This is useful to abstract the actual detail of how we build the entry
+    tuple for caller who don't care about it.
+
+    This should always be called using keyword arguments. Some arguments have
+    default value, this match the value used by index version that does not store such data.
+    """
+    return (
+        offset_type(data_offset, flags),
+        data_compressed_length,
+        data_uncompressed_length,
+        data_delta_base,
+        link_rev,
+        parent_rev_1,
+        parent_rev_2,
+        node_id,
+        sidedata_offset,
+        sidedata_compressed_length,
+        data_compression_mode,
+        sidedata_compression_mode,
+    )

mercurial/revlogutils/constants.py

@@ -12,6 +12,7 b' from __future__ import absolute_import'
 import struct
 
 from ..interfaces import repository
+from .. import revlogutils
 
 ### Internal utily constants
 
@@ -229,7 +230,7 b' COMP_MODE_DEFAULT = 1'
 
 # Chunk use a compression mode stored "inline" at the start of the chunk
 # itself.  This is the mode always used for revlog version "0" and "1"
-COMP_MODE_INLINE = 2
+COMP_MODE_INLINE = revlogutils.COMP_MODE_INLINE
 
 SUPPORTED_FLAGS = {
     REVLOGV0: REVLOGV0_FLAGS,