Consistently install prerequisites from any scope by default

It is also now possible to adjust this behavior with global
config.install.scope override. Valid values for this variable
are:

  project -- only from project
  strong  -- from strong amalgamation
  weak    -- from weak amalgamation
  global  -- from all projects (default)

1 files changed, 32 insertions, 0 deletions

diff --git a/libbuild2/install/utility.cxx b/libbuild2/install/utility.cxx
new file mode 100644
index 0000000..12215f8
--- /dev/null
+++ b/libbuild2/install/utility.cxx
@@ -0,0 +1,32 @@
+// file      : libbuild2/install/utility.cxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#include <libbuild2/install/utility.hxx>
+
+namespace build2
+{
+  namespace install
+  {
+    const scope*
+    install_scope (const target& t)
+    {
+      context& ctx (t.ctx);
+
+      const variable& var (*ctx.var_pool.find ("config.install.scope"));
+
+      if (const string* s = cast_null<string> (ctx.global_scope[var]))
+      {
+        if (*s == "project")
+          return &t.root_scope ();
+        else if (*s == "strong")
+          return &t.strong_scope ();
+        else if (*s == "weak")
+          return &t.weak_scope ();
+        else if (*s != "global")
+          fail << "invalid " << var << " value '" << *s << "'";
+      }
+
+      return nullptr;
+    }
+  }
+}