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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 (not yet included)

Support for using darcs as a backend is being worked on by Thomas Schwinge.

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.)