[[PageOutline(2-3)]] = Mercurial Plugin for Trac (#1847) = There is an '''experimental''' plugin for Trac [milestone:0.10] and Trac [milestone:0.11] which enables [http://www.selenic.com/mercurial Mercurial] to be used instead of [http://subversion.tigris.org Subversion] as the VersioningSystemBackend for Trac. ''The plugin being experimental, expect some rough edges and a somewhat unstable set of features/documentation...'' Change Logs: * log:sandbox/mercurial-plugin * log:sandbox/mercurial-plugin-0.11 * log:sandbox/mercurial-plugin-0.12 (for the MultipleRepositorySupport branch) == Download and Installation == === Trac === ==== Trac 0.10 ==== The plugin [source:sandbox/mercurial-plugin] works fine with Trac 0.10.3, though it will lack the "quickjump" to a branch or tag feature (this was implemented in source:sandbox/vc-refactoring, but is only available in the mainline for 0.11). See TracDownload and install Trac the usual way (see TracInstall) The plugin itself is available from source:sandbox/mercurial-plugin Check it out: {{{ svn co http://svn.edgewall.com/repos/trac/sandbox/mercurial-plugin }}} and create an "egg" from there {{{ $ cd mercurial-plugin $ python setup.py bdist_egg }}} ==== Trac 0.11 ==== There's a newer version of the plugin [source:sandbox/mercurial-plugin-0.11] which has been adapted to work with the trunk version of Trac ([milestone:0.11]dev) and is kept in sync with it. One of the advantage of using this version is that you won't need to install ClearSilver anymore; instead you'll need the Genshi template engine (which is Python only, and therefore straightforward to install). That version of the Mercurial plugin also supports of the new features added in 0.11 to the TracBrowser: - quickjump to a tag or branch - blame support - custom property renderers ([source:sandbox/property-renderers-tmp], not yet in trunk) {{{ svn co http://svn.edgewall.com/repos/trac/trunk trac svn co http://svn.edgewall.org/repos/genshi/trunk genshi }}} and install from there: {{{ $ cd trac $ python setup.py install $ cd .. $ cd genshi $ python setup.py install }}} (for Genshi, you might prefer to use a packaged release, see Genshi:GenshiDownload, or to easy_install it) Then, you need the plugin itself: {{{ svn co http://svn.edgewall.com/repos/trac/sandbox/mercurial-plugin-0.11 }}} create an "egg" from there: {{{ $ cd mercurial-plugin-0.11 $ python setup.py bdist_egg }}} Note that you'll need [http://peak.telecommunity.com/DevCenter/setuptools setuptools] >= 0.6 for that (I used setuptools-0.6a9). ==== Releases ==== || '''Version''' || mercurial-plugin || Trac vc-refactoring || Compatible with hg || || ''0.12.0.0'' || [source:sandbox/mercurial-plugin-0.12] || [source:sandbox/multirepos] ('''not''' trunk) || 0.9.x, 1.0.x, tip ? || ||'''0.11.0.4''' || [source:sandbox/mercurial-plugin-0.11] || [milestone:0.11] or [source:branches/0.11-stable] || 0.9.x, 1.0.x, tip || || ''0.10.0.2'' || [source:sandbox/mercurial-plugin] (0.10) || [milestone:0.10] || 0.7, 0.8, 0.9 || || 0.2 || '''r3014''' || [source:trunk@2900] || 0.7, 0.8, tip || || 0.2 || '''r2905''' || '''r2905''' || 0.7, 0.8, tip || || || r2620 || r2620 || 0.7, tip with 1d7d0c07 || || 0.1 || r2514 || r2511 || 0.7, tip without 1d7d0c07 || Note: - '''the ''Compatible with hg'' column above needs to be updated''' [[br]] It is quite likely that some 0.9.x versions (maybe even 0.9.5) won't work anymore with the 0.11 and 0.12 versions of the plugin (i.e. those are the version actively maintained) - the 0.12 version is somewhat experimental at this point ''worksforme'' - the original branch ([source:sandbox/mercurial-plugin]) which is only for Trac 0.10 is not actively maintained anymore (patches still accepted if you happen to fix a bug, of course) - 0.9.1 was reported not to work with the 0.11 version of the plugin - 0.9.4 (and probably quite a few intermediate changesets between 0.9.3 and 0.9.4) interferes badly with the TH:AccountManager plugin when using Python 2.3.5. It's not unlikely that other setups can be affected by the problem, as basically any code that relies on trapping the `ImportError`, after the `mercurial.demandimport` mechanism has been activated, will fail. If you happen to have this problem (`TypeError: 'unloaded module' object is not callable`}, you need at least r5766/r5767. See also [http://www.selenic.com/mercurial/bts/issue605 issue605]. === Mercurial === The plugin has been tested with recent development versions of Mercurial (upto Changeset 3324:34f08b8883cf from http://selenic.com/hg) and also with Mercurial 0.7 and 0.8. '''It won't work with earlier versions, in particular not with 0.6x.''' The plugin for 0.11 takes benefit of some new features introduced after the 0.8.2 release of Mercurial, and therefore needs at least a 0.9 version of Mercurial. Note: as mentioned here [http://groups.google.com/group/trac-users/browse_thread/thread/9b1cd95621c19921/9f829e8acd958a8e] It *does* require mercurial-0.9.5. Mercurial 0.9.3 is confirmed to not work with plugin 0.11. You can download Mercurial itself from [http://www.selenic.com/mercurial/wiki/index.cgi/Download Hg:Download]. On Windows, it looks like it's possible to re-use the Mercurial library coming from the [Mercurial:BinaryPackages installer], see [http://selenic.com/pipermail/mercurial/2007-July/013827.html this mail] (though to my knowledge, it is not possible to achieve this using PYTHONPATH and PATH: it fails with `ImportError: No module named handlers` due to library.zip coming in the sys.path before the standard library). == Configuration == The configuration has to be done on the Trac side, there's nothing to do on the Mercurial repository side, except for the fact that the repository should be made accessible as a local repository. Thanks to the distributed nature of Mercurial, that's always possible (if the repository is not already local, simply `hg clone` it). === Setting up the mercurial plugin === The TracMercurial plugin egg should be added to the `plugins` folder of the environment, or it can be globally installed (`python setup.py install` or a `python setup.py develop`). For general instructions about plugins, see also TracPlugins. If you installed the egg globally and you're modifying an existing Trac environment to use the Mercurial backend, then you have to explicitly ''enable'' the plugin in TracIni. For the 0.10 plugin, this is done like that: {{{ [components] tracvc.hg.* = enabled }}} Since the 0.11 of the plugin, the package has been renamed to `tracext`: {{{ [components] tracext.hg.* = enabled }}} === Setting up a Trac environment === You can either reuse an existing Trac environment, or create a brand new one. For general instructions, see TracInstall. Since [milestone:0.10], the TracAdmin `initenv` command has now a ''repository type'' argument besides ''repository directory''. For the ''repository type'', specify `hg` instead of the default `svn`. For the ''repository directory'', specify the location of the Mercurial repository (without the ending `.hg`). Your [wiki:TracIni /conf/trac.ini] configuration file should have a `[trac]` section similar to the following: {{{ [trac] repository_type = hg repository_dir = /path/to/my/hg/repository }}} There's also a few Mercurial specific settings in TracIni: {{{ [hg] # -- Show revision number in addition to the changeset hash show_rev = yes # -- Changeset hash format node_format = short # hex: Show the full SHA1 hash # short: Show a shortened hash for the changesets }}} == Features == The Mercurial support is pretty basic, but works well. I've tested that on the Mercurial repository itself and the performance is acceptable, even if there's currently ''no'' caching in the database (this is what I'm going to work on next). Don't even think about using the plugin on a Linux-kernel-sized Mercurial repository, you'll probably burn your disk and/or CPUs ;) For those used to Subversion in general and Subversion repository browsing in Trac in particular, there are a few differences worth noting. === Mercurial Changesets === ==== Changeset Navigation ==== In Mercurial, the ''Previous Changeset''/''Next Changeset'' navigation is ''not'' purely sequential, as it is in Subversion. Instead of a ''flat'' history of successive changesets, we actually navigate a DAG of changesets. This means a changeset can have multiple parents (0, 1 or 2) and multiple children as well (0 to n). Therefore, ''Previous Changeset'' is a link to the first parent, and ''Next Changeset'' is a link to the first child. In case there are additional parents or children, these are shown as additional changeset properties (''Parents'' or ''Children''), placed below the ''Author'' property and above the ''Message'' property. [[Image(hg-plugin-changeset.png)]] Another additional changeset property is the list of ''Tags'' that might be associated with a changeset. ==== Wiki syntax ==== The Wiki syntax has been extended a bit, to cope with the hexadecimal notation of hg changesets. E.g `[8ef2]` would link to the changeset 8ef2ba892518c115170398ec754bd1c27cab271f ... Plain changeset numbers are also recognized, provided they are long enough (12 to 40). Also, it is possible to refer to changesets using the changeset: prefix (or cset: or chgset:, for hgweb compatibility). The tag: prefix can be used to refer to symbolic tags, although this is not a requirement (using. e.g. `cset:tip` would work too). Finally, the branch: prefix has a special meaning, as this will not select the specified revision, but the head which is reachable from that revision. === TracBrowser changes in [milestone:0.11] === The TracBrowser ''View revision'' form has been extended with pulldown menus for jumping to a given tag or branch (in Mercurial, a branch within a repository corresponds to a head, i.e. a changeset without children): ---- [[Image(hg-plugin-browser.png)]] ---- There's also support for visual ''blame'' annotations: ---- [[Image(hg-plugin-annotate.png)]] === Mercurial Queue === Since r6443, the MQ extension is supported. If you happen to have applied mq patches in your repository, Trac will show the corresponding patch names as '''Tags:''' in the changeset view. Also, with the 0.12 branch of the plugin (and the MultipleRepositorySupport branch of Trac), you can browse jointly the main repository and the repository for the associated Mercurial queue, if any (i.e. if you versioned your patch queue using `hg qinit -c` and `hg qcommit`). Furthermore, if you declare such a mercurial repository to be a MQ repository, then all the patches will be correctly rendered as patches, regardless of the patch name (see r6462 for details). == Bugs and Limitations == There are still a lot of things that can be improved. === Features that Trac+svn has but not currently implemented for Trac+hg === * History doesn't follow copy/move operations * No ''path history'' mode (i.e. show all create/delete operations that affected a given path) * Revision log ranges [xxx:yyy] * ~~View arbitrary diffs~~ ''implemented in r6053'' === Multi-repository support === First and foremost, even if Mercurial allows intra-repository branching, it strongly supports the use of branching by cloning the full repository. Therefore, it is common to have a lot of hg repositories around, each devoted to the implementation of some particular feature. Trac should support this by the way of multiple repository support within a single environment (see #2086). '''New''': This is now implemented. Use the 0.12 version of the plugin and the MultipleRepositorySupport. === To cache or not to cache? === When you try TracMercurial on the kernel repo, you quickly realize that it's way too slow without a db! Also, the way the diffs are produced currently (i.e. by Trac, from the full content of the files) is also too slow to be usable on such big repositories (e.g. the kernel changeset fc66195f585a took 7 minutes to be displayed on my machine). See #2591. === Cool Features === ''Wild ideas'' section... ==== Visualize branches and merges ==== There should be a way to show graphically the branch and merge points within the revision log view. Not something as fancy as `hgk`, but nonetheless something that will make the changeset relationships immediately obvious. There's an existing web implementation by Alexander Schremmer: http://moin.pocoo.org:8080/ (select a repo and then 'branchview' button on the top to see it in action) Also, there is [http://trac-hacks.org/wiki/RevtreePlugin RevtreePlugin]. ==== Search over the source ==== A search provider could do the equivalent of an `hg grep`. ==== Highlight Conflict Resolution ==== While visualizing changeset diffs for merge changesets, we already show the changes relative to both parents, which helps to understand how conflicts (if any) were solved. But this can be improved by specifically highlighting lines that differs from both parents. ==== Repository Management ==== Trac should allow for creating new repositories or clones of existing repositories. Maybe repository deletion and renaming should be supported, too. ==== Some Manuals, FAQs and a Forum for this project ==== I am a novice with Aptana/Eclipse and Mercurial. I was hoping this plugin would give me some assistance over the command line interface, but I cannot even understand how to use it from this plug in. I have an existing mercurial repository. What do I do next to use it? A forum might be useful, as I think there is a big audience for a GUI for mercurial, now that firefox has gone to it. ==== HG Forest Support ==== Support for the Forest extension for Mercurial. Forest extension allows operations on trees with nested Mercurial repositories, called forests. Those to some degree correspond to multi-project CVS/Svn/... repositories. Already got most of it working, expect that it's pretty much hacked in the Trac 0.10.3 version of the mercurial plugin. Since it needs a bit more flexibile templating (in regards with the lookup/url's) this is hacked around node.path at the moment. Some (small/large?) issues remain but most of it is working. ''Note that with the MultipleRepositorySupport branch of Trac, it should be possible to implement an IRepositoryProvider component knowing about the `forest` extension and adding besides the repository for the forest itself, the managed repositories as well.'' ==== ''Add your cool feature here...'' ==== == Troubleshooting == === "unsupported version control system hg" === If you get this message try the following two basic checks first: * From a Python console session try to import the Mercurial module, if all goes well it should not complain: {{{ $ python >>> import mercurial >>> }}} * Log in as an user with `TRAC_ADMIN` permission, and look in the `Admin` pages, `General / Plugins`. Do you see the entry for the !TracMercurial plugin there? If yes, is the !MercurialConnector component enabled? == Implementation Notes == I'm interested in feedback concerning the code, in particular concerning Mercurial. I'm pretty sure I did things in a sub-optimal way, as I was discovering the guts of hg while writing the plugin. Therefore, I'll be pleased to get tips for improvements. '' -- ChristianBoos ''