* Allow options from the Nix config file to be overriden from the

command line (e.g. "--option build-use-chroot true").

src/libmain/shared.cc

@@ -243,6 +243,13 @@ static void initAndRun(int argc, char * * argv)
             maxSilentTime = getIntArg(arg, i, args.end());
         else if (arg == "--no-build-hook")
             useBuildHook = false;
+        else if (arg == "--option") {
+            ++i; if (i == args.end()) throw UsageError("`--option' requires two arguments");
+            string name = *i;
+            ++i; if (i == args.end()) throw UsageError("`--option' requires two arguments");
+            string value = *i;
+            overrideSetting(name, tokenizeString(value));
+        }
         else remaining.push_back(arg);
     }
 

src/libstore/globals.cc

@@ -34,6 +34,9 @@ static bool settingsRead = false;
 
 static std::map<string, Strings> settings;
 
+/* Overriden settings. */
+std::map<string, Strings> settingsCmdline;
+
 
 string & at(Strings & ss, unsigned int n)
 {
@@ -74,6 +77,8 @@ static void readSettings()
         settings[name] = Strings(i, tokens.end());
     };
 
+    settings.insert(settingsCmdline.begin(), settingsCmdline.end());
+    
     settingsRead = true;
 }
 
@@ -118,6 +123,13 @@ unsigned int queryIntSetting(const string & name, unsigned int def)
 }
 
 
+void overrideSetting(const string & name, const Strings & value)
+{
+    if (settingsRead) settings[name] = value;
+    settingsCmdline[name] = value;
+}
+
+
 void reloadSettings()
 {
     settingsRead = false;

src/libstore/globals.hh

@@ -101,6 +101,8 @@ bool queryBoolSetting(const string & name, bool def);
 
 unsigned int queryIntSetting(const string & name, unsigned int def);
 
+void overrideSetting(const string & name, const Strings & value);
+
 void reloadSettings();