* New primop builtins.filterSource, which can be used to filter files

  from a source directory.  All files for which a predicate function
  returns true are copied to the store.  Typical example is to leave
  out the .svn directory:

    stdenv.mkDerivation {
      ...
      src = builtins.filterSource
        (path: baseNameOf (toString path) != ".svn")
        ./source-dir;
      # as opposed to
      #   src = ./source-dir;
    }

  This is important because the .svn directory influences the hash in
  a rather unpredictable and variable way.

1 files changed, 4 insertions, 1 deletions

diff --git a/src/libutil/hash.hh b/src/libutil/hash.hh
index 74ae51db32..78227fb6a3 100644
--- a/src/libutil/hash.hh
+++ b/src/libutil/hash.hh
@@ -69,7 +69,10 @@ Hash hashFile(HashType ht, const Path & path);
 
 /* Compute the hash of the given path.  The hash is defined as
    (essentially) hashString(ht, dumpPath(path)). */
-Hash hashPath(HashType ht, const Path & path);
+struct PathFilter;
+extern PathFilter defaultPathFilter;
+Hash hashPath(HashType ht, const Path & path,
+    PathFilter & filter = defaultPathFilter);
 
 /* Compress a hash to the specified number of bytes by cyclically
    XORing bytes together. */