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Diffstat (limited to 'doc')
| -rw-r--r-- | doc/about_rcs_backends.mdwn | 64 |
1 files changed, 61 insertions, 3 deletions
diff --git a/doc/about_rcs_backends.mdwn b/doc/about_rcs_backends.mdwn index 98b5832b6..a878d6daa 100644 --- a/doc/about_rcs_backends.mdwn +++ b/doc/about_rcs_backends.mdwn @@ -178,6 +178,64 @@ please refer to [Emanuele](http://nerd.ocracy.org/em/) ## [[tla]] -## [[bugs/Monotone_rcs_support]] - -Available as an unfinished patch curently. +## [Monotone](http://monotone.ca/) + +There is an unfinished patch in [[bugs/Monotone_rcs_support]]. + +In normal use, monotone has a local database as well as a workspace/working copy. +In ikiwiki terms, the local database takes the role of the master repository, and +the srcdir is the workspace. As all monotone workspaces point to a default +database, there is no need to tell ikiwiki explicitly about the "master" database. It +will know. (BTW - this is also true of subversion. It might be possible to simplify the svn config?) + +The patch currently supports normal committing and getting the history of the page. +To understand the parallel commit approach, you need to understand monotone's +approach to conflicts: + +Monotone allows multiple micro-branches in the database. There is a command, +`mtn merge`, that takes the heads of all these branches and merges them back together +(turning the tree of branches into a dag). Conflicts in monotone (at time of writing) +need to be resolved interactively during this merge process. +It is important to note that having multiple heads is not an error condition in a +monotone database. This condition will occur in normal use. In this case +'update' will choose a head if it can, or complain and tell the user to merge. + +For the ikiwiki plugin, the monotone ikiwiki plugin borrows some ideas from the svn ikiwiki plugin. +On prepedit() we record the revision that this change is based on (I'll refer to this as the prepedit revision). When the web user +saves the page, we check if that is still the current revision. If it is, then we commit. +If it isn't then we check to see if there were any changes by anyone else to the file +we're editing while we've been editing (a diff bewteen the prepedit revision and the current rev). +If there were no changes to the file we're editing then we commit as normal. +All of this should work with the current patch. + +It is only if there have been parallel changes to the file we're trying to commit that +things get hairy. In this case the current (implemented but untested) approach is to +commit the web changes as a branch from the prepedit revision. This +will leave the repository with multiple heads. At this stage, all data is saved, but there +is no way to resolve the potential conflict using the web interface. + +In the specific case of a branch caused by a web edit, it may be possible to +make monotone use the current web interface. This may be possible because we +know that merging between the two revisions we have (the new branch +and the prepedit revision) involves at most one conflicted file. +We could use `mtn explicit_merge` to merge the revisions. If that +succeeds without conflicts then good. If that fails, then we could +use a special lua merge hook to spit out the conflict marked file +and hand it back to the web interface and then abort the merge. At the same time, we'd have +to modify the 'prepedit' data to include both parents so that when +the user saves again we know we're in this case. + +If you get a commit and your prepedit data includes two revids then +we form a commit manually using the automate interface - same way +we currently build the micro-branch. However, while conflicts were being resolved, +someone could have come +along and introduced *another* one. So after forming this merge revision, +you need to go back and check to see if the workspace revision has changed +and possibly go through the whole process again. The repeats until you're +merged. + +The end result of all of this is a system that can resolve all web conflicts without race +conditions. (And because of the way monotone works it saves all data, including +both sides of the merge, before the merge. You can go back later and check that +the merge was reasonable.) It still doesn't provide a web-based way of merging multiple +heads that come in through non-web interaction with monotone. |