Add support for darcs repositories.

src/sql/hydra.sql

@@ -322,6 +322,15 @@ create table CachedGitInputs (
     primary key   (uri, branch, revision)
 );
 
+create table CachedDarcsInputs (
+    uri           text not null,
+    revision      text not null,
+    sha256hash    text not null,
+    storePath     text not null,
+    revCount      integer not null,
+    primary key   (uri, revision)
+);
+
 create table CachedHgInputs (
     uri           text not null,
     branch        text not null,