Improve nested operations support

The idea is this: we need to be able to override "conditional, inner
for outer" recipes with the "unconditional inner" ones. Here is the
concrete scenario: we have {update, test} action and the lib{} target
that is both mentioned as a prerequisite of ./ and exe{}, which is a
test. At first, we want to ignore lib{} when reached as a prerequisite
of ./. But then we get to it via exe{} (which is a test and thus should
be updated). At this point we should override the recipe for lib{} with
the one that would update it rather than ignore.

1 files changed, 14 insertions, 0 deletions

diff --git a/build/operation b/build/operation
index 75d6526..6fde9fd 100644
--- a/build/operation
+++ b/build/operation
@@ -79,6 +79,19 @@ namespace build
     action_id outer_id;
   };
 
+  // This is an "overrides" comparison, i.e., it returns true
+  // if the recipe for x overrides recipe for y. The idea is
+  // that for the same inner operation, action with an outer
+  // operation is "weaker" than the one without.
+  //
+  inline bool
+  operator> (action x, action y)
+  {
+    return x.inner_id != y.inner_id ||
+      (x.outer_id != y.outer_id && y.outer_id != 0);
+  }
+
+  /*
   inline bool
   operator== (action x, action y)
   {
@@ -87,6 +100,7 @@ namespace build
 
   inline bool
   operator!= (action x, action y) {return !(x == y);}
+  */
 
   std::ostream&
   operator<< (std::ostream&, action);