439 

   440   $ cd ..

   441 

   442 In repositories that have accumulated a large number of files over time, the

   443 fncache file is going to be large. If we possibly can avoid loading it, so much the better.

   444 The cache should not loaded when committing changes to existing files, or when unbundling

   445 changesets that only contain changes to existing files:

   446 

   447   $ cat > fncacheloadwarn.py << EOF

   448   > from __future__ import absolute_import

   449   > from mercurial import extensions, store

   450   > 

   451   > def extsetup(ui):

   452   >     def wrapstore(orig, requirements, *args):

   453   >         store = orig(requirements, *args)

   454   >         if 'store' in requirements and 'fncache' in requirements:

   455   >             instrumentfncachestore(store, ui)

   456   >         return store

   457   >     extensions.wrapfunction(store, 'store', wrapstore)

   458   > 

   459   > def instrumentfncachestore(fncachestore, ui):

   460   >     class instrumentedfncache(type(fncachestore.fncache)):

   461   >         def _load(self):

   462   >             ui.warn('fncache load triggered!\n')

   463   >             super(instrumentedfncache, self)._load()

   464   >     fncachestore.fncache.__class__ = instrumentedfncache

   465   > EOF

   466 

   467   $ fncachextpath=`pwd`/fncacheloadwarn.py

   468   $ hg init nofncacheload

   469   $ cd nofncacheload

   470   $ printf "[extensions]\nfncacheloadwarn=$fncachextpath\n" >> .hg/hgrc

   471 

   472 A new file should trigger a load, as we'd want to update the fncache set in that case:

   473 

   474   $ touch foo

   475   $ hg ci -qAm foo

   476   fncache load triggered!

   477 

   478 But modifying that file should not:

   479 

   480   $ echo bar >> foo

   481   $ hg ci -qm foo

   482 

   483 If a transaction has been aborted, the zero-size truncated index file will

   484 not prevent the fncache from being loaded; rather than actually abort

   485 a transaction, we simulate the situation by creating a zero-size index file:

   486 

   487   $ touch .hg/store/data/bar.i

   488   $ touch bar

   489   $ hg ci -qAm bar

   490   fncache load triggered!

   491 

   492 Unbundling should follow the same rules; existing files should not cause a load:

   493 

   494   $ hg clone -q . tobundle

   495   $ echo 'new line' > tobundle/bar

   496   $ hg -R tobundle ci -qm bar

   497   $ hg -R tobundle bundle -q barupdated.hg

   498   $ hg unbundle -q barupdated.hg

   499 

   500 but adding new files should:

   501 

   502   $ touch tobundle/newfile

   503   $ hg -R tobundle ci -qAm newfile

   504   $ hg -R tobundle bundle -q newfile.hg

   505   $ hg unbundle -q newfile.hg

   506   fncache load triggered!

   507 

   508   $ cd ..