Different behaviour in poll and inotify backend

[panglesd]

Continuing my issue streak :)

In polling mode, the whole directory watched is re-traversed and md5summed every $n$ seconds. All file changes, including in subdirectories, trigger a callback.
In inotify mode, the current directory is watched by inotify and only changes in this directory trigger a callback (but a whole scan at the beginning is still done: #41)

Thus, the behaviour is different. Here is an example:

let callback filename =
  Format.printf "modification to %s\n%!" filename;
  Lwt.return ()

let hook =
  if Sys.argv.(1) = "polling" then
    Irmin_watcher__.Core.hook (Lazy.force Irmin_watcher__Polling.v)
  else Irmin_watcher.hook

let never_ends =
  let wait, _ = Lwt.wait () in
  wait

let () =
  let parent = "./" in
  let open Lwt.Syntax in
  Lwt_main.run
  @@
  let* _cancel = hook 0 parent callback in
  never_ends

Now, call this in polling mode, in a directory , and modify a file in a subdirectory (bin/aaa):

$ ./_build/default/bin/main.exe "polling"
modification to bin/aaa

And the same in inotify mode:

$ ./_build/default/bin/main.exe "inotify"

no modification detected

[samoht]

@panglesd patches are welcome :-) I'm re-opeining the issue as it was automatically when you pushed the fixes on your vendored versions.

[panglesd]

Great! I'll be happy to contribute.

I initially decided to vendor and modify irmin-watcher since, while I am pretty sure what behavior I want in my specific case, I am not sure what should be the behavior of this library.

So, currently:

• polling mode watches the directory recursively (eg including sub*directories)
• inotify mode watches only the current directory
• FSEvents watches the directory recursively (IIUC as I don't have a Mac to test. Could someone with a Mac test my snippet above?)

In my specific cases, I want to watch for a specific set of files, so I modified the polling mode to watch a directory non-recursively (I still need to do the same conversion for FSEvents, when I have a Mac...).

In the irmin-watcher, I guess that the "recursive" nature is on purpose? So, the "goal" would be to turn the inotify backend to be recursive? Could you confirm that?