Pass configuration settings to the substituters

Previously substituters could read nix.conf themselves, but this
didn't take --option flags into account.

perl/lib/Nix/Config.pm.in

@@ -19,6 +19,14 @@ $useBindings = "@perlbindings@" eq "yes";
 %config = ();
 
 sub readConfig {
+    if (defined $ENV{'_NIX_OPTIONS'}) {
+        foreach my $s (split '\n', $ENV{'_NIX_OPTIONS'}) {
+            my ($n, $v) = split '=', $s, 2;
+            $config{$n} = $v;
+        }
+        return;
+    }
+
     my $config = "$confDir/nix.conf";
     return unless -f $config;
 

src/libstore/build.cc

@@ -2494,6 +2494,10 @@ void SubstitutionGoal::tryToRun()
             outPipe.readSide.close();
             outPipe.writeSide.close();
 
+            /* Pass configuration options (including those overriden
+               with --option) to the substituter. */
+            setenv("_NIX_OPTIONS", packSettings().c_str(), 1);
+
             /* Fill in the arguments. */
             Strings args;
             args.push_back(baseNameOf(sub));

src/libstore/globals.cc

@@ -36,10 +36,12 @@ bool printBuildTrace = false;
 
 static bool settingsRead = false;
 
-static std::map<string, Strings> settings;
+typedef std::map<string, Strings> Settings;
+
+static Settings settings;
 
 /* Overriden settings. */
-std::map<string, Strings> settingsCmdline;
+Settings settingsCmdline;
 
 
 string & at(Strings & ss, unsigned int n)
@@ -90,7 +92,7 @@ static void readSettings()
 Strings querySetting(const string & name, const Strings & def)
 {
     if (!settingsRead) readSettings();
-    std::map<string, Strings>::iterator i = settings.find(name);
+    Settings::iterator i = settings.find(name);
     return i == settings.end() ? def : i->second;
 }
 
@@ -170,4 +172,15 @@ void setDefaultsFromEnvironment()
 }
 
 
+string packSettings()
+{
+    string s;
+    if (!settingsRead) readSettings();
+    foreach (Settings::iterator, i, settings) {
+        s += i->first; s += '='; s += concatStringsSep(" ", i->second); s += '\n';
+    }
+    return s;
+}
+
+
 }

src/libstore/globals.hh

@@ -115,5 +115,7 @@ void reloadSettings();
 
 void setDefaultsFromEnvironment();
 
+string packSettings();
+
 
 }

src/libstore/local-store.cc

@@ -931,6 +931,10 @@ void LocalStore::startSubstituter(const Path & substituter, RunningSubstituter &
                written in Perl (i.e. all of them) fail. */
             unsetenv("DYLD_LIBRARY_PATH");
 
+            /* Pass configuration options (including those overriden
+               with --option) to the substituter. */
+            setenv("_NIX_OPTIONS", packSettings().c_str(), 1);
+
             fromPipe.readSide.close();
             toPipe.writeSide.close();
             if (dup2(toPipe.readSide, STDIN_FILENO) == -1)