[MirageOS-devel] [ANN] release of Irmin 0.12.0 and introducing irmin-watcher

[Thomas Gazagnaire <thomas@xxxxxxxxxxxxxx>]

Hi all, 

I am in the process of releasing Irmin 0.12.0[1] which brings support for 
native file-system watchers, to improve the performance of watches.

Previously, an Irmin apps who wanted to use watches would set-up file-system 
scanning/polling by doing:

    let () = Irmin_unix.install_dir_polling_listener 1.

which would scan the `.git/refs` directory every second. This was working but 
it was slow (if you are unlucky you might wait for 1s for the watch callbacks 
to trigger) and disk/CPU intensive as we were scanning the full directory every 
second to detect file changes: in case you have 1000s of tags, this could 
easily saturate your CPU (in case you wonder, yes, we really have Git 
repositories with 1000s of tags).

In the 0.12.0 new world, you would do:

    let () = Irmin_unix.set_listen_dir_hook ()

and it will do "the right thing". E.g. if you are on linux, and have the 
`inotify` package installed, it will use libinotify to get notified by the 
kernel on every change and it will re-scan the whole directory. On OSX, if you 
have the `osx-fsevents package installed, it will do the same thing using OSX 
fsevents library. The portable compatibility layer between inotify and fsevents 
comes with `irmin-watcher`[2] that I have just released as well.

Best,
Thomas

[1]: https://github.com/mirage/irmin/releases/tag/0.12.0
[2]: https://github.com/samoht/irmin-watcher/releases/tag/0.2.0

CHANGES:

Irmin 0.12.0

* Depends on irmin-watcher 0.2.0 to use portable file-system watches
  (fsevents on OSX or inotify on Linux) to replace the slow and CPU
  intensive file-system polling that was the default (#380, @samoht)
* Do not use `Lwt_unix.fork` in the tests anymore (#383, @samoht)
* Switch from Stringext to Astring (#382, @samoht)
* Fix regression in the tests for using Git over HTTP (#376, @samoht)
* Catch top-level exceptions in watch callbacks (#375, @samoht)
* Fix merge of assoc list with no common ancestor (#374, @samoht)
* Improve documentation for Git bare repositories (#363, @kayceesrk)
* New functor `Make_with_metadata` to customize the type of the
  nodes metadata (#364, @samoht)
* Remove mentions of private modules from the public interface
  (#364, @samoht)

Irmin-watcher 0.2.0

- Allow to watch non-existing directories (#8, @samoht)
- Expose `Irmin_watches.stats` to get stats about the numbers
  of active watchdogs, and callback dispatchers (#7, @samoht)
- When using fsevents/inotify do not scan the whole tree everytime
  (#6, @samoht)
- Use realpath(3) on Linux and GetFullPathName on Windows to
  normalise the path to watch (#6, @samoht)
- inotify: close the inotify file descriptor when stopping the
  watch (#6. @samoht)
- inotify: fix the path of watched events (inotify uses relative
  patch, unless fsevents which uses absolute paths) (#6, @samoht)
- fix detection of removed files (#6, @samoht)



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