X-Git-Url: http://git.vanrenterghem.biz/git.ikiwiki.info.git/blobdiff_plain/3e55b09a0680e80dd274bf3f455a58c81c3b7984..8c0d441fee35d6d5ba50d8cae65d9166aeecabfd:/doc/about_rcs_backends.mdwn diff --git a/doc/about_rcs_backends.mdwn b/doc/about_rcs_backends.mdwn index 547f973e2..678be2e57 100644 --- a/doc/about_rcs_backends.mdwn +++ b/doc/about_rcs_backends.mdwn @@ -1,16 +1,16 @@ -## A few bits about the RCS backends +# A few bits about the RCS backends -### Terminology +## Terminology ``web-edit'' means that a page is edited by using the web (CGI) interface as opposed to using a editor and the RCS interface. -### [[Subversion]] +## [[Subversion]] -Subversion was that first RCS to be supported by ikiwiki. +Subversion was the first RCS to be supported by ikiwiki. -#### How does it work internally? +### How does it work internally? Master repository M. @@ -22,15 +22,18 @@ HTML is generated from W. rcs_update() will update from M to W. CGI operates on W. rcs_commit() will commit from W to M. +For all the gory details of how ikiwiki handles this behind the scenes, +see [[commit-internals]]. + You browse and web-edit the wiki on W. -### [darcs](http://darcs.net/) (not yet included) +## [darcs](http://darcs.net/) (not yet included) Support for using darcs as a backend is being worked on by [Thomas Schwinge](mailto:tschwinge@gnu.org). -#### How will it work internally? +### How will it work internally? ``Master'' repository R1. @@ -45,27 +48,75 @@ There is a working copy of R1: R2. CGI operates on R2. rcs_commit() will push from R2 to R1. You browse the wiki on R1 and web-edit it on R2. This means for example -that R2 needs to be updated from R1 if you are going the web-edit a page, +that R2 needs to be updated from R1 if you are going to web-edit a page, as the user otherwise might be irritated otherwise... How do changes get from R1 to R2? Currently only internally in -rcs_commit(). Is rcs_prepedit() suitable? +rcs\_commit(). Is rcs\_prepedit() suitable? It follows that the HTML rendering and the CGI handling can be completely separated parts in ikiwiki. -##### Rationale for doing it differently than in the Subversion case +What repository should [[RecentChanges]] and [[History]] work on? R1? + +#### Rationale for doing it differently than in the Subversion case darcs is a distributed RCS, which means that every checkout of a repository is equal to the repository it was checked-out from. There is no forced hierarchy. -R1 is the nevertheless called the master repository. It's used for +R1 is nevertheless called the master repository. It's used for collecting all the changes and publishing them: on the one hand via the rendered HTML and on the other via the standard darcs RCS interface. -R2, the repository where CGI operates on, is just a checkout of R1 and +R2, the repository the CGI operates on, is just a checkout of R1 and doesn't really differ from the other checkouts that people will branch off from R1. (To be continued.) + +#### Another possible approach + +Here's what I (tuomov) think, would be a “cleaner” approach: + + 1. Upon starting to edit, Ikiwiki gets a copy of the page, and `darcs changes --context`. + This context _and_ the present version of the page are stored in as the “version” of the + page in a hidden control of the HTML. + Thus the HTML includes all that is needed to generate a patch wrt. to the state of the + repository at the time the edit was started. This is of course all that darcs needs. + 2. Once the user is done with editing, _Ikiwiki generates a patch bundle_ for darcs. + This should be easy with existing `Text::Diff` or somesuch modules, as the Web edits + only concern single files. The reason why the old version of the page is stored in + the HTML (possibly compressed) is that the diff can be generated. + 3. Now this patch bundle is applied with `darcs apply`, or sent by email for moderation… + there are many possibilities. + +This approach avoids some of the problems of concurrent edits that the previous one may have, +although there may be conflicts, which may or may not propagate to the displayed web page. +(Unfortunately there is not an option to `darcs apply` to generate some sort of ‘confliction resolution +bundle’.) Also, only one repository is needed, as it is never directly modified +by Ikiwiki. + +This approach might be applicable to other distributed VCSs as well, although they're not as oriented +towards transmitting changes with standalone patch bundles (often by email) as darcs is. + +## [[Git]] + +Regarding the Git support, Recai says: + +I have been testing it for the past few days and it seems satisfactory. I +haven't observed any race condition regarding the concurrent blog commits +and it handles merge conflicts gracefully as far as I can see. + +As you may notice from the patch size, GIT support is not so trivial to +implement (for me, at least). Being a fairly fresh code base it has some +bugs. It also has some drawbacks (especially wrt merge which was the hard +part). GIT doesn't have a similar functionality like 'svn merge -rOLD:NEW +FILE' (please see the relevant comment in mergepast for more details), so I +had to invent an ugly hack just for the purpose. + +## [mercurial](http://www.selenic.com/mercurial/) + +Being worked on by Emanuele Aina. + +