bdiff: early pruning of common prefix before doing expensive computations
It seems quite common that files don't change completely. New lines are often
pretty much appended, and modifications will often only change a small section
of the file which on average will be in the middle.
There can thus be a big win by pruning a common prefix before starting the more
expensive search for longest common substrings.
Worst case, it will scan through a long sequence of similar bytes without
encountering a newline. Splitlines will then have to do the same again ...
twice for each side. If similar lines are found, splitlines will save the
double iteration and hashing of the lines ... plus there will be less lines to
find common substrings in.
This change might in some cases make the algorith pick shorter or less optimal
common substrings. We can't have the cake and eat it.
This make hg --time bundle --base null -r 4.0 go from 14.5 to 15 s - a 3%
increase.
On mozilla-unified:
perfbdiff -m 3041e4d59df2
! wall 0.053088 comb 0.060000 user 0.060000 sys 0.000000 (best of 100) to
! wall 0.024618 comb 0.020000 user 0.020000 sys 0.000000 (best of 116)
perfbdiff 0e9928989e9c --alldata --count 10
! wall 0.702075 comb 0.700000 user 0.700000 sys 0.000000 (best of 15) to
! wall 0.579235 comb 0.580000 user 0.580000 sys 0.000000 (best of 18)
Mercurial's internal web server, hgweb, can serve either a single
repository, or a tree of repositories. In the second case, repository
paths and global options can be defined using a dedicated
configuration file common to :hg:`serve`, ``hgweb.wsgi``,
``hgweb.cgi`` and ``hgweb.fcgi``.
This file uses the same syntax as other Mercurial configuration files
but recognizes only the following sections:
- web
- paths
- collections
The ``web`` options are thoroughly described in :hg:`help config`.
The ``paths`` section maps URL paths to paths of repositories in the
filesystem. hgweb will not expose the filesystem directly - only
Mercurial repositories can be published and only according to the
configuration.
The left hand side is the path in the URL. Note that hgweb reserves
subpaths like ``rev`` or ``file``, try using different names for
nested repositories to avoid confusing effects.
The right hand side is the path in the filesystem. If the specified
path ends with ``*`` or ``**`` the filesystem will be searched
recursively for repositories below that point.
With ``*`` it will not recurse into the repositories it finds (except for
``.hg/patches``).
With ``**`` it will also search inside repository working directories
and possibly find subrepositories.
In this example::
[paths]
/projects/a = /srv/tmprepos/a
/projects/b = c:/repos/b
/ = /srv/repos/*
/user/bob = /home/bob/repos/**
- The first two entries make two repositories in different directories
appear under the same directory in the web interface
- The third entry will publish every Mercurial repository found in
``/srv/repos/``, for instance the repository ``/srv/repos/quux/``
will appear as ``http://server/quux/``
- The fourth entry will publish both ``http://server/user/bob/quux/``
and ``http://server/user/bob/quux/testsubrepo/``
The ``collections`` section is deprecated and has been superseded by
``paths``.
URLs and Common Arguments
=========================
URLs under each repository have the form ``/{command}[/{arguments}]``
where ``{command}`` represents the name of a command or handler and
``{arguments}`` represents any number of additional URL parameters
to that command.
The web server has a default style associated with it. Styles map to
a collection of named templates. Each template is used to render a
specific piece of data, such as a changeset or diff.
The style for the current request can be overwritten two ways. First,
if ``{command}`` contains a hyphen (``-``), the text before the hyphen
defines the style. For example, ``/atom-log`` will render the ``log``
command handler with the ``atom`` style. The second way to set the
style is with the ``style`` query string argument. For example,
``/log?style=atom``. The hyphenated URL parameter is preferred.
Not all templates are available for all styles. Attempting to use
a style that doesn't have all templates defined may result in an error
rendering the page.
Many commands take a ``{revision}`` URL parameter. This defines the
changeset to operate on. This is commonly specified as the short,
12 digit hexadecimal abbreviation for the full 40 character unique
revision identifier. However, any value described by
:hg:`help revisions` typically works.
Commands and URLs
=================
The following web commands and their URLs are available:
.. webcommandsmarker