Revert back to only cleaning targets in subdirectories

Cleaning everything as long as it is in the same strong amalgamation had
some undesirable side effects. For example, in bpkg, upgrading a package
(which requires clean/reconfigure) led to all its prerequisite being
cleaned as well and then rebuilt. That was very surprising.

3 files changed, 8 insertions, 22 deletions

diff --git a/build2/algorithm.ixx b/build2/algorithm.ixx
index 19eb7e7..a405c30 100644
--- a/build2/algorithm.ixx
+++ b/build2/algorithm.ixx
@@ -101,11 +101,7 @@ namespace build2
   search_and_match_prerequisites (action a, target& t)
   {
     search_and_match_prerequisites (
-      a,
-      t,
-      a.operation () != clean_id
-      ? dir_path ()
-      : t.strong_scope ().out_path ());
+      a, t, a.operation () != clean_id ? dir_path () : t.dir);
   }
 
   inline void
@@ -118,7 +114,7 @@ namespace build2
       // through groups since the group target should clean eveything
       // up. A bit of an optimization.
       //
-      search_and_match_prerequisites (a, t, t.strong_scope ().out_path ());
+      search_and_match_prerequisites (a, t, t.dir);
   }
 
   target_state
diff --git a/build2/cxx/compile.cxx b/build2/cxx/compile.cxx
index a1abfcb..22a25cb 100644
--- a/build2/cxx/compile.cxx
+++ b/build2/cxx/compile.cxx
@@ -78,13 +78,8 @@ namespace build2
       // code (below) takes care of the ones it is adding.
       //
       // When cleaning, ignore prerequisites that are not in the same
-      // or a subdirectory of our strong amalgamation.
+      // or a subdirectory of ours.
       //
-      const dir_path* amlg (
-        a.operation () != clean_id
-        ? nullptr
-        : &t.strong_scope ().out_path ());
-
       link::search_paths_cache lib_paths; // Extract lazily.
 
       for (prerequisite_member p: group_prerequisite_members (a, t))
@@ -117,7 +112,7 @@ namespace build2
 
         target& pt (p.search ());
 
-        if (a.operation () == clean_id && !pt.dir.sub (*amlg))
+        if (a.operation () == clean_id && !pt.dir.sub (t.dir))
           continue;
 
         build2::match (a, pt);
diff --git a/build2/cxx/link.cxx b/build2/cxx/link.cxx
index 42b2235..3b5b857 100644
--- a/build2/cxx/link.cxx
+++ b/build2/cxx/link.cxx
@@ -545,13 +545,8 @@ namespace build2
       // files as well as search and match.
       //
       // When cleaning, ignore prerequisites that are not in the same
-      // or a subdirectory of our strong amalgamation.
+      // or a subdirectory of ours.
       //
-      const dir_path* amlg (
-        a.operation () != clean_id
-        ? nullptr
-        : &t.strong_scope ().out_path ());
-
       for (prerequisite_member p: group_prerequisite_members (a, t))
       {
         bool group (!p.prerequisite.belongs (t)); // Group's prerequisite.
@@ -569,7 +564,7 @@ namespace build2
           if (pt == nullptr)
             pt = &p.search ();
 
-          if (a.operation () == clean_id && !pt->dir.sub (*amlg))
+          if (a.operation () == clean_id && !pt->dir.sub (t.dir))
             continue; // Skip.
 
           // If this is the obj{} or lib{} target group, then pick the
@@ -631,9 +626,9 @@ namespace build2
         target& ot (search (o_type, d, *cp.tk.name, nullptr, cp.scope));
 
         // If we are cleaning, check that this target is in the same or
-        // a subdirectory of our strong amalgamation.
+        // a subdirectory of ours.
         //
-        if (a.operation () == clean_id && !ot.dir.sub (*amlg))
+        if (a.operation () == clean_id && !ot.dir.sub (t.dir))
         {
           // If we shouldn't clean obj{}, then it is fair to assume
           // we shouldn't clean cxx{} either (generated source will