CONTRIBUTORS

hg: make cachedlocalrepo cache appropriate repoview object

Before this patch, 'cachedlocalrepo' always caches "visible" repoview
object, because 'cachedlocalrepo' uses "visible" repoview returned by
'hg.repository()' without any additional processing.

If the client of 'cachedlocalrepo' wants "served" repoview, some
objects to be cached are discarded unintentionally.

    1. 'cachedlocalrepo' newly caches "visible" repoview object
       (call it VIEW1)

    2. 'cachedlocalrepo' returns VIEW1 to the client of it at 'fetch()'

    3. the client gets "served" repoview object by 'filtered("served")'
       on VIEW1 (call this "served" repoview VIEW2)

    4. accessing to 'repo.changelog' implies:
       - instantiation of changelog via 'localrepository.changelog'
       - instantiation of "filtered changelog" via 'repoview.changelog'

    5. "filtered changelog" above is cached in VIEW2

    6. VIEW2 is discarded after processing, because there is no
       reference to it

    7. 'cachedlocalrepo' returns VIEW1 cached at (1) above to the
       client at next 'fetch()'

    8. 'filtered("served")' on VIEW1 at the client side creates new
       "served" repoview again, because VIEW1 is "visible"
       (call this new "served" repoview VIEW3)

    9. accessing to 'repo.changelog' implies instantiation of filtered
       changelog again, because "filtered changelog" is cached in
       VIEW2 at (5), but not in VIEW3 currently used

    10. (go to (7) above)

As described above, "served" repoview object and "filtered changelog"
cached in it are discarded always, even if the repository itself
hasn't been changed since last access.

For example, in the case of 'hgweb_mod.hgweb', "newly caching" occurs,
when:

  - all cached objects are already assigned to another threads
    (in this case, repoview is created in 'cachedlocalrepo.copy()')

  - or, stat of '00changelog.i' is changed from last access
    (in this case, repoview is created in 'cachedlocalrepo.fetch()')

    once changes are pushed via HTTP, this always occurs.

The root cause of this inefficiency is that 'cachedlocalrepo' always
caches "visible" repoview object, even if the client of it wants
another view.

To make 'cachedlocalrepo' cache appropriate repoview object, this
patch adds additional filtering on the repo object returned by
'hg.repository()'. It is assumed that initial repoview object should
be already filtered by expected view.

After this patch:

  - 'filtered("served")' on VIEW1 at (3)/(7) above returns VIEW1
    itself, because VIEW1 is now "served", and

  - VIEW2 and VIEW3 equal VIEW1

  - therefore, "filtered changelog" is cached in VIEW1, and reused
    intentionally

[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>