In pkg-build make sure that reconfiguring dependent doesn't change current dependency selection

Also fix the dependency alternative selection so that if the dependency
package of a different version is already being built, then make sure that one
of them is satisfactory for all the dependents and don't consider this
alternative if that's not the case.

1 files changed, 7 insertions, 0 deletions

diff --git a/bpkg/pkg-configure.hxx b/bpkg/pkg-configure.hxx
index 5d6b2eb..23dab83 100644
--- a/bpkg/pkg-configure.hxx
+++ b/bpkg/pkg-configure.hxx
@@ -37,6 +37,12 @@ namespace bpkg
   // dependency alternatives lists are allowed and are ignored (see pkg-build
   // for the use-case).
   //
+  // If prerequisites corresponding to the previous configured state of the
+  // package are specified, then for each depends value try to select an
+  // alternative where dependencies all belong to this list (the "recreate
+  // dependency decisions" mode). Failed that, select an alternative as if no
+  // prerequisites are specified (the "make dependency decisions" mode).
+  //
   void
   pkg_configure (const common_options&,
                  database&,
@@ -44,6 +50,7 @@ namespace bpkg
                  const shared_ptr<selected_package>&,
                  const dependencies&,
                  package_skeleton&&,
+                 const vector<package_name>* prerequisites,
                  bool simulate,
                  const function<find_database_function>& = {});