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diff --git a/doc/design/assistant/blog/day_156_and_157__direct_mode_assistant.mdwn b/doc/design/assistant/blog/day_156_and_157__direct_mode_assistant.mdwn new file mode 100644 index 000000000..76df1f510 --- /dev/null +++ b/doc/design/assistant/blog/day_156_and_157__direct_mode_assistant.mdwn @@ -0,0 +1,49 @@ +Over Christmas, I'm working on making the assistant support direct +mode. I like to have a fairly detailed plan before starting this kind of +job, but in this case, I don't. (Also I have a cold so planning? Meh.) +This is a process of seeing what's broken in direct mode and fixing it. +I don't know if it'll be easy or hard. Let's find out.. + +* First, got direct mode adding of new files working. This was not hard, all the + pieces I needed were there. For now, it uses the same method as in + indirect mode to make sure nothing can modify the file while it's being added. + +* An unexpected problem is that in its startup scan, the assistant runs + `git add --update` to detect and stage any deletions that happened + while it was not running. But in direct mode that also stages the full file + contents, so can't be used. Had to switch to using git plumbing to only + stage deleted files. Happily this also led to fixing a bug, where deletions + were not always committed at startup. + +* Next, got it to commit when direct mode files are modified. The Watcher + thread gets a inotify event when this happens, so that was easy. (Although + in doing that I had to disable a guard in direct mode that made annexed + files co-exist with regular in-git files, so such mixed repositories + probably won't work in direct mode yet.) + + However, naughty kqueue is another story, there are no kqueue events for + file modifications. So this won't work on OSX or the BSDs yet. I tried + setting some more kqueue flags in hope that one would make such events + appear, but no luck. Seems I will need to find some other method to detect + file modifications, possibly an OSX-specific API. + +* Another unexpected problem: When an assistant receives new files from one + of its remotes, in direct mode it still sets up symlinks to the content. + This was because the Merger thread didn't use the `sync` command's direct + mode aware merge code. + + One other interesting thing about file transfers in + direct mode is that they can sometimes happen before the git branch is + pushed and merged. When that happens the object is stored in indirect mode. + Happily the direct mode aware merger detects such objects and converts them + to direct mode. + +* Noticed that when the assistant adds a new object for a modified direct + mode file, it neglects to update the mapping for old object, so it + incorrectly still maps that object to the file. That bad data could lead to + unknown buggy behavior. + + This is complicated by a mapping only being maintained from objects to + files, but not a reverse mapping. To get from files to objects currently + requires querying git for the symlink target, which is relatively slow. + |