feat(BSS2): use releases-ebrains to track releases

This adapts to the new releases-ebrains repo which tracks, for every BrainScaleS toplevel package (pynn-brainscales, hxtorch, jaxsnn, oppulance), the state of of all dependent repo states via git submodules. We initialize only those submodules which are needed for the individual toplevel.

packages/build-brainscales/package.py

@@ -15,10 +15,20 @@ import spack.build_environment
 class BuildBrainscales(WafPackage):
     """Common stuff for BrainScaleS packages..."""
 
+    version(
+        "9.0-a4",
+        git="https://github.com/electronicvisions/releases-ebrains",
+        tag="ebrains-9.0-a4",
+        submodules=True, # the "submodules" parameter isn't part of the source cache key/name
+    )
+
     # waf setup performs git clone and might query gerrit
     depends_on('git', type=('build', 'link'))
     depends_on('py-git-review', type=('build', 'link'))
 
+    # old BrainScaleS EBRAINS releases used `waf setup --project=X` to download
+    # sources of the dependent repositories
+    @when("@:8")
     def do_fetch(self, mirror_only=False):
         """Setup the project."""
 
@@ -56,6 +66,16 @@ class BuildBrainscales(WafPackage):
         with unittest.mock.patch('spack.fetch_strategy.GitFetchStrategy.archive', new=custom_archive):
             self.stage.cache_local()
 
+    # new BrainScaleS EBRAINS releases use git submodules to download sources;
+    # we still need to keep the `.git/` folders of the submodules in the source cache though
+    @when("@9:")
+    def do_fetch(self, mirror_only=False):
+        # in the configure step, we need access to all archived .git folders
+        def custom_archive(self, destination):
+            super(spack.fetch_strategy.GitFetchStrategy, self).archive(destination)
+        with unittest.mock.patch('spack.fetch_strategy.GitFetchStrategy.archive', new=custom_archive):
+            super(BuildBrainscales, self).do_fetch(mirror_only)
+
     def _setup_common_env(self, env):
         # grenade needs to find some libraries for the JIT-compilation of
         # programs for BrainScaleS-2's embedded processor.
@@ -112,6 +132,9 @@ class BuildBrainscales(WafPackage):
 
         args = ['--prefix={0}'.format(self.prefix)]
         args += self.configure_args()
+
+        if spec.version >= Version("9"):
+            self.waf('setup', '--directory=' + str(spec.name), '--repo-db-url=https://github.com/electronicvisions/projects')
         self.waf('configure', '--build-profile=release', '--disable-doxygen', *args)
 
     def build_args(self):