* In nix-store: added query `--referers-closure' that returns the

  closure of the referers relation rather than the references
  relation, i.e., the set of all paths that directly or indirectly
  refer to the given path.  Note that contrary to the references
  closure this set is not fixed; it can change as paths are added to
  or removed from the store.

4 files changed, 27 insertions, 9 deletions

diff --git a/src/libstore/build.hh b/src/libstore/build.hh
index ed83d678ec66..52e7c9b9d5de 100644
--- a/src/libstore/build.hh
+++ b/src/libstore/build.hh
@@ -21,9 +21,12 @@ Derivation derivationFromPath(const Path & drvPath);
 
 /* Place in `paths' the set of all store paths in the file system
    closure of `storePath'; that is, all paths than can be directly or
-   indirectly reached from it.  `paths' is not cleared. */
+   indirectly reached from it.  `paths' is not cleared.  If
+   `flipDirection' is true, the set of paths that can reach
+   `storePath' is returned; that is, the closures under the `referers'
+   relation instead of the `references' relation is returned. */
 void computeFSClosure(const Path & storePath,
-    PathSet & paths);
+    PathSet & paths, bool flipDirection = false);
 
 /* Place in `paths' the set of paths that are required to `realise'
    the given store path, i.e., all paths necessary for valid
diff --git a/src/libstore/misc.cc b/src/libstore/misc.cc
index dbb9273f7955..802e576512f1 100644
--- a/src/libstore/misc.cc
+++ b/src/libstore/misc.cc
@@ -12,17 +12,20 @@ Derivation derivationFromPath(const Path & drvPath)
 
 
 void computeFSClosure(const Path & storePath,
-    PathSet & paths)
+    PathSet & paths, bool flipDirection)
 {
     if (paths.find(storePath) != paths.end()) return;
     paths.insert(storePath);
 
     PathSet references;
-    queryReferences(storePath, references);
+    if (flipDirection)
+        queryReferers(storePath, references);
+    else
+        queryReferences(storePath, references);
 
     for (PathSet::iterator i = references.begin();
          i != references.end(); ++i)
-        computeFSClosure(*i, paths);
+        computeFSClosure(*i, paths, flipDirection);
 }
 
 
diff --git a/src/nix-store/help.txt b/src/nix-store/help.txt
index deef23ff8f3b..35d5423cd8d2 100644
--- a/src/nix-store/help.txt
+++ b/src/nix-store/help.txt
@@ -4,7 +4,8 @@ nix-store [OPTIONS...] [ARGUMENTS...]
 
 Operations:
 
-  --realise / -r: build a Nix derivation
+  --realise / -r: ensure path validity; if a derivation, ensure that
+      validity of the outputs
   --add / -A: copy a path to the Nix store
   --query / -q: query information
 
@@ -27,9 +28,16 @@ Query flags:
   --outputs: query the output paths of a Nix derivation (default)
   --requisites / -R: print all paths necessary to realise a path
   --references: print all paths referenced by the given path
-  --referers: print all paths refering to the given path
+  --referers: print all paths directly refering to the given path
+  --referers-closure: print all paths (in)directly refering to the given path
   --graph: print a dot graph rooted at given ids
 
+Query switches (not applicable to all queries):
+
+  --use-output: perform query on output of derivation, not derivation itself
+  --force-realise: realise the path before performing the query
+  --include-outputs: in `-R' on a derivation, include requisites of outputs
+  
 Options:
 
   --verbose / -v: verbose operation (may be repeated)
diff --git a/src/nix-store/main.cc b/src/nix-store/main.cc
index addf9c7d0d67..dc7a6de8b8ec 100644
--- a/src/nix-store/main.cc
+++ b/src/nix-store/main.cc
@@ -96,7 +96,8 @@ static void printPathSet(const PathSet & paths)
 /* Perform various sorts of queries. */
 static void opQuery(Strings opFlags, Strings opArgs)
 {
-    enum { qOutputs, qRequisites, qReferences, qReferers, qGraph } query = qOutputs;
+    enum { qOutputs, qRequisites, qReferences, qReferers,
+           qReferersClosure, qGraph } query = qOutputs;
     bool useOutput = false;
     bool includeOutputs = false;
     bool forceRealise = false;
@@ -107,6 +108,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
         else if (*i == "--requisites" || *i == "-R") query = qRequisites;
         else if (*i == "--references") query = qReferences;
         else if (*i == "--referers") query = qReferers;
+        else if (*i == "--referers-closure") query = qReferersClosure;
         else if (*i == "--graph") query = qGraph;
         else if (*i == "--use-output" || *i == "-u") useOutput = true;
         else if (*i == "--force-realise" || *i == "-f") forceRealise = true;
@@ -128,7 +130,8 @@ static void opQuery(Strings opFlags, Strings opArgs)
 
         case qRequisites:
         case qReferences:
-        case qReferers: {
+        case qReferers:
+        case qReferersClosure: {
             PathSet paths;
             for (Strings::iterator i = opArgs.begin();
                  i != opArgs.end(); i++)
@@ -138,6 +141,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
                     storePathRequisites(path, includeOutputs, paths);
                 else if (query == qReferences) queryReferences(path, paths);
                 else if (query == qReferers) queryReferers(path,  paths);
+                else if (query == qReferersClosure) computeFSClosure(path, paths, true);
             }
             printPathSet(paths);
             break;