# A few bits about the RCS backends ## 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 was the first RCS to be supported by ikiwiki. ### How does it work internally? Master repository M. RCS commits from the outside are installed into M. There is a working copy of M (a checkout of M): W. 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) Support for using darcs as a backend is being worked on by [Thomas Schwinge](mailto:tschwinge@gnu.org). ### How will it work internally? ``Master'' repository R1. RCS commits from the outside are installed into R1. HTML is generated from R1. HTML is automatically generated (by using a ``post-hook'') each time a new change is installed into R1. It follows that rcs_update() is not needed. 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 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? It follows that the HTML rendering and the CGI handling can be completely separated parts in ikiwiki. 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 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 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.) ## [[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.