Include the output name in the GC root link

Output names are now appended to resulting GC symlinks, e.g. by
nix-build.  For backwards compatibility, if the output is named "out",
nothing is appended.  E.g. doing "nix-build -A foo" on a derivation
that produces outputs "out", "bin" and "dev" will produce symlinks
"./result", "./result-bin" and "./result-dev", respectively.

scripts/nix-build.in

@@ -46,7 +46,7 @@ Flags:
   --no-out-link: do not create the `result' symlink
   --out-link / -o NAME: create symlink NAME instead of `result'
   --attr / -A ATTR: select a specific attribute from the Nix expression
-  
+
   --run-env: build dependencies of the specified derivation, then start a
       shell with the environment of the derivation
   --command: command to run with `--run-env'
@@ -114,7 +114,7 @@ EOF
         push @buildArgs, "--dry-run";
         $dryRun = 1;
     }
-    
+
     elsif ($arg eq "--show-trace") {
         push @instArgs, $arg;
     }
@@ -122,22 +122,22 @@ EOF
     elsif ($arg eq "-") {
         @exprs = ("-");
     }
-    
+
     elsif ($arg eq "--verbose" or substr($arg, 0, 2) eq "-v") {
         push @buildArgs, $arg;
         push @instArgs, $arg;
         $verbose = 1;
     }
-    
+
     elsif ($arg eq "--quiet") {
         push @buildArgs, $arg;
         push @instArgs, $arg;
     }
-    
+
     elsif ($arg eq "--run-env") {
         $runEnv = 1;
     }
-    
+
     elsif ($arg eq "--command") {
         $n++;
         die "$0: `$arg' requires an argument\n" unless $n < scalar @ARGV;

src/libmain/shared.cc

@@ -33,16 +33,6 @@ static void sigintHandler(int signo)
 }
 
 
-Path makeRootName(const Path & gcRoot, int & counter)
-{
-    counter++;
-    if (counter == 1)
-        return gcRoot;
-    else
-        return (format("%1%-%2%") % gcRoot % counter).str();
-}
-
-
 void printGCWarning()
 {
     static bool haveWarned = false;

src/libmain/shared.hh

@@ -26,7 +26,6 @@ MakeError(UsageError, nix::Error);
 class StoreAPI;
 
 /* Ugh.  No better place to put this. */
-Path makeRootName(const Path & gcRoot, int & counter);
 void printGCWarning();
 
 void printMissing(StoreAPI & store, const PathSet & paths);

src/nix-instantiate/nix-instantiate.cc

@@ -64,9 +64,11 @@ void processExpr(EvalState & state, const Strings & attrPaths,
                     Path drvPath = i->queryDrvPath(state);
                     if (gcRoot == "")
                         printGCWarning();
-                    else
+                    else {
-                        drvPath = addPermRoot(*store, drvPath,
+                        Path rootName = gcRoot;
-                            makeRootName(gcRoot, rootNr), indirectRoot);
+                        if (++rootNr > 1) rootName += "-" + int2String(rootNr);
+                        drvPath = addPermRoot(*store, drvPath, rootName, indirectRoot);
+                    }
                     std::cout << format("%1%\n") % drvPath;
                 }
             }

src/nix-store/nix-store.cc

@@ -64,15 +64,19 @@ static PathSet realisePath(const Path & path)
     if (isDerivation(path)) {
         store->buildPaths(singleton<PathSet>(path));
         Derivation drv = derivationFromPath(*store, path);
+        rootNr++;
 
         PathSet outputs;
         foreach (DerivationOutputs::iterator, i, drv.outputs) {
             Path outPath = i->second.path;
             if (gcRoot == "")
                 printGCWarning();
-            else
+            else {
-                outPath = addPermRoot(*store, outPath,
+                Path rootName = gcRoot;
-                    makeRootName(gcRoot, rootNr), indirectRoot);
+                if (rootNr > 1) rootName += "-" + int2String(rootNr);
+                if (i->first != "out") rootName += "-" + i->first;
+                outPath = addPermRoot(*store, outPath, rootName, indirectRoot);
+            }
             outputs.insert(outPath);
         }
         return outputs;