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revlog: change generaldelta delta parent heuristic...
revlog: change generaldelta delta parent heuristic The old generaldelta heuristic was "if p1 (or p2) was closer than the last full text, use it, otherwise use prev". This was problematic when a repo contained multiple branches that were very different. If commits to branch A were pushed, and the last full text was branch B, it would generate a fulltext. Then if branch B was pushed, it would generate another fulltext. The problem is that the last fulltext (and delta'ing against `prev` in general) has no correlation with the contents of the incoming revision, and therefore will always have degenerate cases. According to the blame, that algorithm was chosen to minimize the chain length. Since there is already code that protects against that (the delta-vs-fulltext code), and since it has been improved since the original generaldelta algorithm went in (2011), I believe the chain length criteria will still be preserved. The new algorithm always diffs against p1 (or p2 if it's closer), unless the resulting delta will fail the delta-vs-fulltext check, in which case we delta against prev. Some before and after stats on manifest.d size. internal large repo old heuristic - 2.0 GB new heuristic - 1.2 GB mozilla-central old heuristic - 242 MB new heuristic - 261 MB The regression in mozilla central is due to the new heuristic choosing p2r as the delta when it's closer to the tip. Switching the algorithm to always prefer p1r brings the size back down (242 MB). This is result of the way in which mozilla does merges and pushes, and the result could easily swing the other direction in other repos (depending on if they merge X into Y or Y into X), but will never be as degenerate as before. I future patch will address the regression by introducing an optional, even more aggressive delta heuristic which will knock the mozilla manifest size down dramatically.

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patchreview.txt
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*patchreview.txt* Vim global plugin for doing single, multi-patch or diff code reviews
Version v0.2.2 (for Vim version 7.0 or higher)
Author: Manpreet Singh < junkblocker@yahoo.com >
Copyright (C) 2006-2010 by Manpreet Singh
License : This file is placed in the public domain.
=============================================================================
CONTENTS *patchreview* *diffreview* *patchreview-contents*
1. Contents.........................................: |patchreview-contents|
2. Introduction.....................................: |patchreview-intro|
3. PatchReview options..............................: |patchreview-options|
4. PatchReview Usage................................: |patchreview-usage|
4.1 DiffReview Usage.............................: |:DiffReview|
4.2 PatchReview Usage............................: |:PatchReview|
=============================================================================
PatchReview Introduction *patchreview-intro*
The Patch Review plugin allows easy single or multipatch code or diff reviews.
It opens each affected file in the patch or in a workspace diff in a diff view
in a separate tab.
VIM provides the |:diffpatch| and related commands to do single file reviews
but can not handle patch files containing multiple patches as is common with
software development projects. This plugin provides that missing
functionality.
It also improves on |:diffpatch|'s behavior of creating the patched files in
the same directory as original file which can lead to project workspace
pollution.
It does automatic diff generation for various version control systems by
running their diff command.
=============================================================================
PatchReview Options *patchreview-options*
g:patchreview_patch = {string}
Optional path to patch binary. PatchReview tries to locate patch on
system path automatically. If the binary is not on system path, this
option tell PatchReview the full path to the binary. This option, if
specified, overrides the default patch binary on the path.
examples:
(On Windows with Cygwin) >
let g:patchreview_patch = 'c:\\cygwin\\bin\\patch.exe'
<
(On *nix systems) >
let g:patchreview_patch = '/usr/bin/gpatch'
<
g:patchreview_filterdiff = {string}
Optional path to filterdiff binary. PatchReview tries to locate
filterdiff on system path automatically. If the binary is not on system
path, this option tell PatchReview the full path to the binary. This
option, if specified, overrides the default filterdiff binary on the
path.
examples:
(On Windows with Cygwin)
>
let g:patchreview_filterdiff = 'c:\\cygwin\\bin\\filterdiff.exe'
<
(On *nix systems)
>
let g:patchreview_filterdiff = '/usr/bin/filterdiff'
<
=============================================================================
PatchReview Usage *patchreview-usage*
*:DiffReview*
:DiffReview
Perform a diff review in the current directory under version control.
Currently supports Mercurial (hg), Subversion (svn), CVS, Bazaar (bzr) and
Monotone.
*:PatchReview*
:PatchReview patchfile_path [optional_source_directory]
Perform a patch review in the current directory based on the supplied
patchfile_path. If optional_source_directory is specified, patchreview is
done on that directory. Otherwise, the current directory is assumed to be
the source directory.
Only supports context or unified format patches.
------------------------------------------------------------------------------
vim: ft=help:ts=2:sts=2:sw=2:tw=78:norl: