Merge branch 'nix'.

This is a squashed commit of the following:

commit 0dccab9f417b406f5d4aedc81900fc7b2f16c9f6
Author: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date:   Thu Jul 2 00:30:16 2015 +0200

    Typo

commit 2cd28517b13524c242c7758783b0b2d8250fdded
Author: Ludovic Courtès <ludo@gnu.org>
Date:   Wed Jul 1 14:56:34 2015 +0200

    Preserve supplementary groups of build users

    The following patch is an attempt to address this bug (see
    <http://bugs.gnu.org/18994>) by preserving the supplementary groups of
    build users in the build environment.

    In practice, I would expect that supplementary groups would contain only
    one or two groups: the build users group, and possibly the “kvm” group.

    [Changed &at(0) to data() and removed tabs - Eelco]

commit 6e38685ef65284093df79ebe7378bac33b0e7e5d
Author: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date:   Tue Jun 30 21:41:26 2015 +0200

    GC: Handle ENOSPC creating/moving to the trash directory

    Issue #564.

commit 5e0a9ae2e25a1016389f4893a6ed6682aadcf51d
Author: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date:   Mon Jun 22 15:54:55 2015 +0200

    Use posix_fallocate to create /nix/var/nix/db/reserved

commit 4e5ab98d6d14f8b0e3bd1d77b2f4f2354e7a49a8
Author: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date:   Mon Jun 22 15:47:40 2015 +0200

    Make /nix/var/nix/db/reserved bigger

    Issue #564.

commit 60bda60fc06135aa97a93301b1a9e2270768f5b3
Author: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date:   Wed Jun 10 16:17:06 2015 +0200

    Export outputPaths function

    This is useful for the new hydra-queue-runner.

commit 5dfea34048aa8541f20aeb2fbcd163561b609a49
Author: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date:   Thu Jul 2 22:51:33 2015 +0200

    Use std::vector::data()

commit 2459458bc8257734ca78cb7a2db3df20bd730ec0
Author: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date:   Thu Jun 4 16:04:41 2015 +0200

    Allow substitutes for builds that have preferLocalBuild set

    Not substituting builds with "preferLocalBuild = true" was a bad idea,
    because it didn't take the cost of dependencies into account. For
    instance, if we can't substitute a fetchgit call, then we have to
    download/build git and all its dependencies.

    Partially reverts 5558652709f27e8a887580b77b93c705659d7a4b and adds a
    new derivation attribute "allowSubstitutes" to specify whether a
    derivation may be substituted.

1 files changed, 2 insertions, 2 deletions

diff --git a/nix/libstore/misc.cc b/nix/libstore/misc.cc
index 6ecf8787cf..22363af126 100644
--- a/nix/libstore/misc.cc
+++ b/nix/libstore/misc.cc
@@ -120,7 +120,7 @@ void queryMissing(StoreAPI & store, const PathSet & targets,
                 if (invalid.empty()) continue;
 
                 todoDrv.insert(*i);
-                if (settings.useSubstitutes && !willBuildLocally(drv))
+                if (settings.useSubstitutes && substitutesAllowed(drv))
                     query.insert(invalid.begin(), invalid.end());
             }
 
@@ -144,7 +144,7 @@ void queryMissing(StoreAPI & store, const PathSet & targets,
 
             PathSet outputs;
             bool mustBuild = false;
-            if (settings.useSubstitutes && !willBuildLocally(drv)) {
+            if (settings.useSubstitutes && substitutesAllowed(drv)) {
                 foreach (DerivationOutputs::iterator, j, drv.outputs) {
                     if (!wantOutput(j->first, i2.second)) continue;
                     if (!store.isValidPath(j->second.path)) {