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, 23 insertions, 8 deletions

diff --git a/nix/libstore/gc.cc b/nix/libstore/gc.cc
index 34768324c2..72eff52426 100644
--- a/nix/libstore/gc.cc
+++ b/nix/libstore/gc.cc
@@ -376,6 +376,7 @@ struct LocalStore::GCState
     bool gcKeepOutputs;
     bool gcKeepDerivations;
     unsigned long long bytesInvalidated;
+    bool moveToTrash = true;
     Path trashDir;
     bool shouldDelete;
     GCState(GCResults & results_) : results(results_), bytesInvalidated(0) { }
@@ -428,16 +429,23 @@ void LocalStore::deletePathRecursive(GCState & state, const Path & path)
        not holding the global GC lock) we can delete the path without
        being afraid that the path has become alive again.  Otherwise
        delete it right away. */
-    if (S_ISDIR(st.st_mode)) {
+    if (state.moveToTrash && S_ISDIR(st.st_mode)) {
         // Estimate the amount freed using the narSize field.  FIXME:
         // if the path was not valid, need to determine the actual
         // size.
-        state.bytesInvalidated += size;
-        if (chmod(path.c_str(), st.st_mode | S_IWUSR) == -1)
-            throw SysError(format("making `%1%' writable") % path);
-        Path tmp = state.trashDir + "/" + baseNameOf(path);
-        if (rename(path.c_str(), tmp.c_str()))
-            throw SysError(format("unable to rename `%1%' to `%2%'") % path % tmp);
+        try {
+            if (chmod(path.c_str(), st.st_mode | S_IWUSR) == -1)
+                throw SysError(format("making `%1%' writable") % path);
+            Path tmp = state.trashDir + "/" + baseNameOf(path);
+            if (rename(path.c_str(), tmp.c_str()))
+                throw SysError(format("unable to rename `%1%' to `%2%'") % path % tmp);
+            state.bytesInvalidated += size;
+        } catch (SysError & e) {
+            if (e.errNo == ENOSPC) {
+                printMsg(lvlInfo, format("note: can't create move `%1%': %2%") % path % e.msg());
+                deleteGarbage(state, path);
+            }
+        }
     } else
         deleteGarbage(state, path);
 
@@ -636,7 +644,14 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
 
     if (state.shouldDelete) {
         if (pathExists(state.trashDir)) deleteGarbage(state, state.trashDir);
-        createDirs(state.trashDir);
+        try {
+            createDirs(state.trashDir);
+        } catch (SysError & e) {
+            if (e.errNo == ENOSPC) {
+                printMsg(lvlInfo, format("note: can't create trash directory: %1%") % e.msg());
+                state.moveToTrash = false;
+            }
+        }
     }
 
     /* Now either delete all garbage paths, or just the specified