CONTRIBUTORS

fsmonitor: hook up state-enter, state-leave signals

Keeping the codebase in sync with upstream:

Watchman 4.4 introduced an advanced settling feature that allows publishing
tools to notify subscribing tools of the boundaries for important filesystem
operations.

https://facebook.github.io/watchman/docs/cmd/subscribe.html#advanced-settling
has more information about how this feature works.

This diff connects a signal that we're calling `hg.update` to the mercurial
update function so that mercurial can indirectly notify tools (such as IDEs or
build machinery) when it is changing the working copy.  This will allow those
tools to pause their normal actions as the files are changing and defer them
until the end of the operation.

In addition to sending the enter/leave signals for the state, we are able to
publish useful metadata along the same channel.  In this case we are passing
the following pieces of information:

1. destination revision hash
2. An estimate of the distance between the current state and the target state
3. A success indicator.
4. Whether it is a partial update

The distance is estimate may be useful to tools that wish to change their
strategy after the update has complete.  For example, a large update may be
efficient to deal with by walking some internal state in the subscriber rather
than feeding every individual file notification through its normal (small)
delta mechanism.

We estimate the distance by comparing the repository revision number.  In some
cases we cannot come up with a number so we report 0.  This is ok; we're
offering this for informational purposes only and don't guarantee its accuracy.

The success indicator is only really meaningful when we generate the
state-leave notification; it indicates the overall success of the update.

[This file is here for historical purposes, all recent contributors
should appear in the changelog directly]

Andrea Arcangeli <andrea at suse.de>
Thomas Arendsen Hein <thomas at intevation.de>
Goffredo Baroncelli <kreijack at libero.it>
Muli Ben-Yehuda <mulix at mulix.org>
Mikael Berthe <mikael at lilotux.net>
Benoit Boissinot <bboissin at gmail.com>
Brendan Cully <brendan at kublai.com>
Vincent Danjean <vdanjean.ml at free.fr>
Jake Edge <jake at edge2.net>
Michael Fetterman <michael.fetterman at intel.com>
Edouard Gomez <ed.gomez at free.fr>
Eric Hopper <hopper at omnifarious.org>
Alecs King <alecsk at gmail.com>
Volker Kleinfeld <Volker.Kleinfeld at gmx.de>
Vadim Lebedev <vadim at mbdsys.com>
Christopher Li <hg at chrisli.org>
Chris Mason <mason at suse.com>
Colin McMillen <mcmillen at cs.cmu.edu>
Wojciech Milkowski <wmilkowski at interia.pl>
Chad Netzer <chad.netzer at gmail.com>
Bryan O'Sullivan <bos at serpentine.com>
Vicent Seguí Pascual <vseguip at gmail.com>
Sean Perry <shaleh at speakeasy.net>
Nguyen Anh Quynh <aquynh at gmail.com>
Ollivier Robert <roberto at keltia.freenix.fr>
Alexander Schremmer <alex at alexanderweb.de>
Arun Sharma <arun at sharma-home.net>
Josef "Jeff" Sipek <jeffpc at optonline.net>
Kevin Smith <yarcs at qualitycode.com>
TK Soh <teekaysoh at yahoo.com>
Radoslaw Szkodzinski <astralstorm at gorzow.mm.pl>
Samuel Tardieu <sam at rfc1149.net>
K Thananchayan <thananck at yahoo.com>
Andrew Thompson <andrewkt at aktzero.com>
Michael S. Tsirkin <mst at mellanox.co.il>
Rafael Villar Burke <pachi at mmn-arquitectos.com>
Tristan Wibberley <tristan at wibberley.org>
Mark Williamson <mark.williamson at cl.cam.ac.uk>