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view mercurial/help/diffs.txt @ 24735:07200e3332a1
tags: extract .hgtags filenodes cache to a standalone file
Resolution of .hgtags filenodes values has historically been a
performance pain point for large repositories, where reading individual
manifests can take over 100ms. Multiplied by hundreds or even thousands
of heads and resolving .hgtags filenodes becomes a performance issue.
This patch establishes a standalone cache file holding the .hgtags
filenodes for each changeset. After this patch, the .hgtags filenode
for any particular changeset should only have to be computed once
during the lifetime of the repository.
The introduced hgtagsfnodes1 cache file is modeled after the rev branch
cache: the cache is effectively an array of entries consisting of a
changeset fragment and the filenode for a revision. The file grows in
proportion to the length of the repository (24 bytes per changeset) and
is truncated when the repository is stripped. The file is not written
unless tag info is requested and tags have changed since last time.
This patch partially addresses issue4550. Future patches will split the
"tags" cache file into per-filter files and will refactor the cache
format to not capture the .hgtags fnodes, as these are now stored in
the hgtagsfnodes1 cache. This patch is capable of standing alone. We
should not have to wait on the tags cache filter split and format
refactor for this patch to land.
author | Gregory Szorc <gregory.szorc@gmail.com> |
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date | Wed, 15 Apr 2015 17:42:38 -0400 |
parents | ebfc46929f3e |
children |
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Mercurial's default format for showing changes between two versions of a file is compatible with the unified format of GNU diff, which can be used by GNU patch and many other standard tools. While this standard format is often enough, it does not encode the following information: - executable status and other permission bits - copy or rename information - changes in binary files - creation or deletion of empty files Mercurial also supports the extended diff format from the git VCS which addresses these limitations. The git diff format is not produced by default because a few widespread tools still do not understand this format. This means that when generating diffs from a Mercurial repository (e.g. with :hg:`export`), you should be careful about things like file copies and renames or other things mentioned above, because when applying a standard diff to a different repository, this extra information is lost. Mercurial's internal operations (like push and pull) are not affected by this, because they use an internal binary format for communicating changes. To make Mercurial produce the git extended diff format, use the --git option available for many commands, or set 'git = True' in the [diff] section of your configuration file. You do not need to set this option when importing diffs in this format or using them in the mq extension.