Patch to add --from-file option to nix commands

from-file-option.patch

Index: nix/src/libmain/shared.cc
===================================================================
--- nix/src/libmain/shared.cc	(revision 28396)
+++ nix/src/libmain/shared.cc	(working copy)
@@ -7,6 +7,7 @@
 #include "misc.hh"
 
 #include <iostream>
+#include <fstream>
 #include <cctype>
 #include <exception>
 
@@ -251,6 +252,20 @@
             string value = *i;
             overrideSetting(name, tokenizeString(value));
         }
+        else if (arg == "--from-file") {
+            ++i;
+            if (i == args.end()) throw UsageError("`--from-file' requires an argument");
+            std::ifstream argFile;
+            argFile.open(i->c_str());
+            if (argFile.fail()) {
+              throw Error(format("failed to open option file `%1%'") % *i);
+            }
+            string fileArg;
+            while (argFile >> fileArg) {
+              args.push_back(fileArg);
+            }
+            argFile.close();
+        }
         else remaining.push_back(arg);
     }
 
Index: nix/doc/manual/opt-common.xml
===================================================================
--- nix/doc/manual/opt-common.xml	(revision 28396)
+++ nix/doc/manual/opt-common.xml	(working copy)
@@ -341,6 +341,16 @@
 </varlistentry>
 
 
+<varlistentry><term><option>--from-file</option> <replaceable>file</replaceable></term>
+
+  <listitem><para>This option reads whitespace-separated options
+  from <replacable>file</replacable> and adds them to the argument list.
+  This can be particularly useful if <replacable>file</replacable>
+  is /dev/stdin.</para></listitem>
+
+</varlistentry>
+
+
 </variablelist>