Implement automatic loading of directory buildfiles

Now instead of explicitly writing:

d = foo/ bar/
./: $d
include $d

We can (usually) just write:

./: foo/ bar/

1 files changed, 11 insertions, 3 deletions

diff --git a/build2/file b/build2/file
index 191e3dc..c8d8f6f 100644
--- a/build2/file
+++ b/build2/file
@@ -59,14 +59,14 @@ namespace build2
   source (const path& buildfile, scope& root, scope& base);
 
   // As above but first check if this buildfile has already been sourced for
-  // the base scope.
+  // the base scope. Return false if the file has already been sourced.
   //
-  void
+  bool
   source_once (const path& buildfile, scope& root, scope& base);
 
   // As above but checks against the specified scope rather than base.
   //
-  void
+  bool
   source_once (const path& buildfile, scope& root, scope& base, scope& once);
 
   // Create project's root scope. Only set the src_root variable if the
@@ -88,6 +88,14 @@ namespace build2
               const dir_path& out_base,
               const dir_path& src_base);
 
+  // Return a scope for the specified directory (first). Note that switching
+  // to this scope might also involve switch to a new root scope (second) if
+  // the new scope is in another project. In the new scope is not in any
+  // project, then NULL is returned in second.
+  //
+  pair<scope&, scope*>
+  switch_scope (scope& root, const dir_path&);
+
   // Bootstrap the project's root scope, the out part.
   //
   void