web commit by JoshTriplett: scmbug

[git.ikiwiki.info.git] / doc / about_rcs_backends.mdwn

diff --git a/doc/about_rcs_backends.mdwn b/doc/about_rcs_backends.mdwn
index 16f1692deca3f6cb3148c37ade158175ab4b7e24..6cc8108a7e2163d21052a28263f5d8a405fb33c3 100644 (file)
--- a/doc/about_rcs_backends.mdwn
+++ b/doc/about_rcs_backends.mdwn
@@ -1,16 +1,18 @@
-## A few bits about the RCS backends
+A few bits about the RCS backends

 
 

-### Terminology
+[[toc ]]
+
+## 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.
 
 
 
 ``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 the 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.
 
 
 Master repository M.
 


@@ -28,12 +30,13 @@ see [[commit-internals]].
 You browse and web-edit the wiki on W.
 
 
 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
 
 Support for using darcs as a backend is being worked on by [Thomas

-Schwinge](mailto:tschwinge@gnu.org).
+Schwinge](mailto:tschwinge@gnu.org), although development is on hold curretly.
+There is a patch in the [[patchqueue]].

 
 

-#### How will it work internally?
+### How will it work internally?

 
 ``Master'' repository R1.
 
 
 ``Master'' repository R1.
 


@@ -59,7 +62,7 @@ separated parts in ikiwiki.
 
 What repository should [[RecentChanges]] and [[History]] work on?  R1?
 
 
 What repository should [[RecentChanges]] and [[History]] work on?  R1?
 

-##### Rationale for doing it differently than in the Subversion case
+#### 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
 
 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


@@ -75,10 +78,46 @@ off from R1.
 
 (To be continued.)
 
 
 (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.
+
+> The mercurial plugin seems to just use one repo and edit it directly - is
+> there some reason that's okay there but not for darcs? I agree with tuomov
+> that having just the one repo would be preferable; the point of a dvcs is
+> that there's no difference between one repo and another. I've got a
+> darcs.pm based on mercurial.pm, that's almost usable... --bma

 
 

-### [[git]] (not yet included)
+>> IMHO it comes down to whatever works well for a given RCS. Seems like
+>> the darcs approach _could_ be done with most any distributed system, but
+>> it might be overkill for some (or all?) While there is the incomplete darcs
+>> plugin in the [[patchqueue]], if you submit one that's complete, I will
+>> probably accept it into ikiwiki.. --[[Joey]]

 
 

-A patch with full git support is at <http://people.debian.org/~roktas/patches/ikiwiki/git.patch>. Regarding the patch, Recai says:
+## [[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
 
 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


@@ -91,34 +130,48 @@ 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.
 
 FILE' (please see the relevant comment in mergepast for more details), so I
 had to invent an ugly hack just for the purpose.
 

-Some other notes:
+By design, Git backend uses a "master-clone" repository pair approach in contrast
+to the single repository approach (here, _clone_ may be considered as the working
+copy of a fictious web user).  Even though a single repository implementation is
+possible, it somewhat increases the code complexity of backend (I couldn't figure
+out a uniform method which doesn't depend on the prefered repository model, yet).
+By exploiting the fact that the master repo and _web user_'s repo (`srcdir`) are all
+on the same local machine, I suggest to create the latter with the "`git clone -l -s`"
+command to save disk space.
+
+Note that, as a rule of thumb, you should always put the rcs wrapper (`post-update`)
+into the master repository (`.git/hooks/`) as can be noticed in the Git wrappers of
+the sample [[ikiwiki.setup]].
+
+## [[Mercurial]]

 
 

-- There are two separate helper packages in git.pm. To keep things self
-  confined, I haven't split it up.
+The Mercurial backend is still in a early phase, so it may not be mature 
+enough, but it should be simple to understand and use.

 
 

-- I've used a (mini) Debug.pm during the tests and made it a separate file
-  for the convenience of others.  It relies on the "constant folding"
-  feature of Perl, so there shouldn't be a runtime penalty (at least this
-  is what the 'perl -MO=Deparse shows', haven't made a real benchmark).
+As Mercurial is a distributed RCS, it lacks the distinction between 
+repository and working copy (every wc is a repo).

 
 

-- rcs_notify() has not been implemented yet (I have noticed it after I
-  finished the main work).
+This means that the Mercurial backend uses directly the repository as 
+working copy (the master M and the working copy W described in the svn 
+example are the same thing).
+
+You only need to specify 'srcdir' (the repository M) and 'destdir' (where
+the HTML will be generated).
+
+Master repository M.

 
 

-- GIT backend uses the gitweb for repository browsing (the counterpart of
-  ViewCVS).
+RCS commit from the outside are installed into M.

 
 

-- There might be some subs in GIT name space which you may prefer to move to
-  the main code.
+M is directly used as working copy (M is also W).

 
 

-- Due to the reasons explained in the code, I've written an rcs_invoke()
-  wrapper.  May be there should be a better approach to reach the same
-  goal.
+HTML is generated from the working copy in M. rcs_update() will update 
+to the last committed revision in M (the same as 'hg update').
+If you use an 'update' hook you can generate automatically the HTML
+in the destination directory each time 'hg update' is called.

 
 

-- There are some parts which I may change in future, like using a global
-  rcs_fatal_error and the ugly error reporting code in _rcs_commit.
+CGI operates on M. rcs_commit() will commit directly in M.

 
 

-- Documentation is missing.
+If you have any question or suggestion about the Mercurial backend 
+please refer to [Emanuele](http://nerd.ocracy.org/em/)

 
 

-It works for me, but of course in the end, the final decision is yours (due
-to mostly GIT quirks, the implementation is not clean as SVN).  Feel free
-to fix/delete/add whatever you want.  Hope it doesn't have any serious bug.
\ No newline at end of file
+## [[tla]]