* Applied rbroek's patch from the branch at

https://svn.cs.uu.nl:12443/repos/trace/buildfarm-control/trunk/ext/nix/,
  with some modifications.  This allows `nix-env -qa' to show the
  attribute path that can be used to unambiguously install a package
  using `nix-env -i -A'.  Example:

    $ nix-env -f top-level/all-packages.nix -qaA subversion xorg-server
    subversionWithJava  subversion-1.2.3
    subversion          subversion-1.3.2
    subversion14        subversion-1.4.0pre-rc1
    xorg.xorgserver     xorg-server-1.1.0

src/nix-env/main.cc

@@ -724,6 +724,7 @@ static void opQuery(Globals & globals,
 {
     bool printStatus = false;
     bool printName = true;
+    bool printAttrPath = false;
     bool printSystem = false;
     bool printDrvPath = false;
     bool printOutPath = false;
@@ -747,6 +748,8 @@ static void opQuery(Globals & globals,
         else if (*i == "--available" || *i == "-a") source = sAvailable;
         else throw UsageError(format("unknown flag `%1%'") % *i);
 
+    if (globals.instSource.type == srcAttrPath) printAttrPath = true; /* hack */
+
     if (opArgs.size() == 0) {
         printMsg(lvlInfo, "warning: you probably meant to specify the argument '*' to show all packages");
     }
@@ -809,6 +812,8 @@ static void opQuery(Globals & globals,
                     + (subs.size() > 0 ? "S" : "-"));
             }
 
+            if (printAttrPath) columns.push_back(i->attrPath);
+
             if (printName) columns.push_back(i->name);
 
             if (compareVersions) {