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-rw-r--r--doc/commit-internals.mdwn20
-rw-r--r--doc/features.mdwn3
2 files changed, 23 insertions, 0 deletions
diff --git a/doc/commit-internals.mdwn b/doc/commit-internals.mdwn
new file mode 100644
index 000000000..3a464ffbf
--- /dev/null
+++ b/doc/commit-internals.mdwn
@@ -0,0 +1,20 @@
+Saving this irc transcript here, since it's a fairly in-depth discussion of
+how ikiwiki handles commits, locking, etc, and avoids some races while
+doing so.
+
+ <tschwinge> What happens if I edit a page and in the underground a new version is installed into the svn repository?
+ <tschwinge> The revision when I started editing was saved, right?
+ <joeyh> what happens, exactly is:
+ <joeyh> 1. the new version that was committed first get into svn, and ikiwiki updates its WC to have the new version
+ <joeyh> 2. When you save your edit, ikiwiki detects a conflict.
+ <joeyh> 3. It uses svn merge to try to resolve it; if it's resolved it adds your changes transparently
+ <joeyh> 4. If the conflict needs manual resolution, it displays the page with conflict markers in the editor for you to resolve
+ <tschwinge> Ok.
+ <joeyh> Note that in step 2, it detects the conflict by using svn info to get the current Revision of the page in the WC, and compares that to a revision that is stored when you start to edit the page
+ <joeyh> that's why rcs_prepedit exists, to get that revision info
+ <tschwinge> But isn't there a race condition?
+ <joeyh> well, there is locking going on too
+ <joeyh> ikiwiki won't update the WC in step 1. if another instance of itself is getting the Revision info
+ <tschwinge> Is that lockwiki()?
+ <joeyh> yeah
+ <joeyh> note that when it gets the current Revision info of a page during its conflict detection, svn could have changed the page in the repo, and the WC not been updated yet due to the lock, but this isn't a race since the commit will then fail due to a regular svn conflict and the conflict detction will still work.
diff --git a/doc/features.mdwn b/doc/features.mdwn
index a1a69f22c..e762b27a9 100644
--- a/doc/features.mdwn
+++ b/doc/features.mdwn
@@ -97,6 +97,9 @@ Some of ikiwiki's features:
shown in the file to resolve the conflict, so if you're already familiar
with that there's no new commit marker syntax to learn.
+ For all the gory details of how ikiwiki handles this behind the scenes,
+ see [[commit-internals]].
+
* page locking
Wiki admins can lock pages so that only other admins can edit them.