[PATCH 0 of 7 V2 of F2 series] fncache2 repo format

[Adrian Buehlmann]

This series would create new fncache2 repos. Just for consideration. Not to be pushed.

I've used it to convert a Netbeans repo to the fncache2 format using clone --pull on
Windows 7 x64. It passes verify afterwards.

This series as a whole would bring the Netbeans repo speed from (in fncache format)

  $ hg perffncacheencode
  ! wall 0.853000 comb 0.858006 user 0.858006 sys 0.000000 (best of 12)

down to (in fncache2 format)

  $ hg perffncacheencode
  ! wall 0.244000 comb 0.218401 user 0.218401 sys 0.000000 (best of 41)

Which is ~3.5 times faster.

Compare that with the A2 series, which still uses the current fncache repo format:

  $ hg perffncacheencode
  ! wall 0.488000 comb 0.483603 user 0.483603 sys 0.000000 (best of 21)


I've sent this to get an idea what we could expect from this new encoding and
implementation (speedwise).