test(pkg): local sources in opam repo (ocaml#9583)

Signed-off-by: Rudi Grinberg <me@rgrinberg.com>

test/blackbox-tests/test-cases/pkg/opam-source-conversion.t

@@ -14,11 +14,36 @@ Test conversion of opam sources into lock dir package specifications
   $ solve testpkg
   Solution for dune.lock:
   - testpkg.0.0.1
+
+  $ showpkg() {
+  > local f=dune.lock/testpkg.pkg
+  > [ -e $f ] && cat $f
+  > }
 
-  $ cat dune.lock/testpkg.pkg
+  $ showpkg
   (version 0.0.1)
 
   (source
    (fetch
     (url http://caml.inria.fr/pub/distrib/ocaml-3.11/ocaml-3.11.1.tar.gz)
     (checksum md5=069aa55d40e548280f92af693f6c625a)))
+
+  $ mkdir testpkgsources
+
+  $ mkpkg testpkg <<EOF
+  > url {
+  >   src: "file://$PWD/testpkgsources"
+  > }
+  > EOF
+
+  $ rm -rf dune.lock
+
+  $ solve testpkg 2>&1 | sed -E 's#.*.sandbox/[^/]+#.sandbox/$SANDBOX#g' | sed '/File "/q'
+  Package "testpkg" has source archive which lacks a checksum.
+  The source archive will be downloaded from:
+  .sandbox/$SANDBOX/default/test/blackbox-tests/test-cases/pkg/testpkgsources
+  Dune will compute its own checksum for this source archive.
+  File "vendor/opam/src/repository/opamRepository.ml", line 405, characters 31-37:
+
+  $ showpkg
+  [1]