Turn BuildBranch methods into regular functions

Previously they were generator functions, which yielded interesting
context at interesting times so that the caller could respond by
printing status messages.

The only benefits this had over callbacks were:

1.  1 fewer function scope to worry about. I don't have data on the
    amount of memory used for a function scope vs a generator, but it
    could be less cognitive load for determining which variables are
    defined in the callback's body.
2.  It is possible to yield in the caller, so you could make that into a
    coroutine too, however this wasn't required in this case, as the
    yielded value was intended to be informational.

The downsides to this are:

1.  It's a rather peculiar construct, so can be difficult to understand
    what's going on, and the implications, which led to
2.  If you call the function, but don't use the iterator it returned,
    then it won't do anything, which is very confusing indeed, if you're
    not used to how generator functions work.

3 files changed, 28 insertions, 18 deletions

diff --git a/morphlib/buildbranch.py b/morphlib/buildbranch.py
index d415e7e1..7aa75dc1 100644
--- a/morphlib/buildbranch.py
+++ b/morphlib/buildbranch.py
@@ -84,14 +84,14 @@ class BuildBranch(object):
     def _register_cleanup(self, func, *args, **kwargs):
         self._cleanup.append((func, args, kwargs))
 
-    def add_uncommitted_changes(self):
+    def add_uncommitted_changes(self, add_cb=lambda **kwargs: None):
         '''Add any uncommitted changes to temporary build GitIndexes'''
         for gd, (build_ref, index) in self._to_push.iteritems():
             changed = [to_path for code, to_path, from_path
                        in index.get_uncommitted_changes()]
             if not changed:
                 continue
-            yield gd, build_ref
+            add_cb(gd=gd, build_ref=gd, changed=changed)
             index.add_files_from_working_tree(changed)
 
     @staticmethod
@@ -102,7 +102,7 @@ class BuildBranch(object):
             sha1 = gd.store_blob(loader.save_to_string(morphology))
             yield 0100644, sha1, morphology.filename
 
-    def inject_build_refs(self, loader):
+    def inject_build_refs(self, loader, inject_cb=lambda **kwargs: None):
         '''Update system and stratum morphologies to point to our branch.
 
         For all edited repositories, this alter the temporary GitIndex
@@ -141,12 +141,13 @@ class BuildBranch(object):
         morphs.traverse_specs(process, filter)
 
         if any(m.dirty for m in morphs.morphologies):
-            yield self._root
+            inject_cb(gd=self._root)
 
         self._root_index.add_files_from_index_info(
             self._hash_morphologies(self._root, morphs.morphologies, loader))
 
-    def update_build_refs(self, name, email, uuid):
+    def update_build_refs(self, name, email, uuid,
+                          commit_cb=lambda **kwargs: None):
         '''Commit changes in temporary GitIndexes to temporary branches.
 
         `name` and `email` are required to construct the commit author info.
@@ -176,7 +177,7 @@ class BuildBranch(object):
 
         with morphlib.branchmanager.LocalRefManager() as lrm:
             for gd, (build_ref, index) in self._to_push.iteritems():
-                yield gd, build_ref
+                commit_cb(gd=gd, build_ref=build_ref)
                 tree = index.write_tree()
                 try:
                     parent = gd.resolve_ref_to_commit(build_ref)
@@ -201,7 +202,7 @@ class BuildBranch(object):
                     #       a problem.
                     lrm.update(gd, build_ref, commit, old_commit)
 
-    def push_build_branches(self):
+    def push_build_branches(self, push_cb=lambda **kwargs: None):
         '''Push all temporary build branches to the remote repositories.
 
         This is a no-op if the BuildBranch was constructed with
@@ -219,8 +220,9 @@ class BuildBranch(object):
             with morphlib.branchmanager.RemoteRefManager(False) as rrm:
                 for gd, (build_ref, index) in self._to_push.iteritems():
                     remote = gd.get_remote('origin')
-                    yield gd, build_ref, remote
                     refspec = morphlib.gitdir.RefSpec(build_ref)
+                    push_cb(gd=gd, build_ref=build_ref,
+                            remote=remote, refspec=refspec)
                     rrm.push(remote, refspec)
             self._register_cleanup(rrm.close)
 
diff --git a/morphlib/plugins/build_plugin.py b/morphlib/plugins/build_plugin.py
index 1a4fb573..3a489a61 100644
--- a/morphlib/plugins/build_plugin.py
+++ b/morphlib/plugins/build_plugin.py
@@ -187,27 +187,31 @@ class BuildPlugin(cliapp.Plugin):
         bb = morphlib.buildbranch.BuildBranch(sb, build_ref_prefix,
                                               push_temporary=push)
         with contextlib.closing(bb) as bb:
-
-            for gd, build_ref in bb.add_uncommitted_changes():
+            def report_add(gd, build_ref, changed):
                 self.app.status(msg='Adding uncommitted changes '\
                                     'in %(dirname)s to %(ref)s',
                                 dirname=gd.dirname, ref=build_ref, chatty=True)
+            bb.add_uncommitted_changes(add_cb=report_add)
 
-            for gd in bb.inject_build_refs(loader):
+            def report_inject(gd):
                 self.app.status(msg='Injecting temporary build refs '\
                                     'into morphologies in %(dirname)s',
                                 dirname=gd.dirname, chatty=True)
+            bb.inject_build_refs(loader, inject_cb=report_inject)
 
-            for gd, build_ref in bb.update_build_refs(name, email, build_uuid):
+            def report_commit(gd, build_ref):
                 self.app.status(msg='Committing changes in %(dirname)s '\
                                     'to %(ref)s',
                                 dirname=gd.dirname, ref=build_ref, chatty=True)
+            bb.update_build_refs(name, email, build_uuid,
+                                 commit_cb=report_commit)
 
-            for gd, build_ref, remote in bb.push_build_branches():
+            def report_push(gd, build_ref, remote, refspec):
                 self.app.status(msg='Pushing %(ref)s in %(dirname)s '\
                                     'to %(remote)s',
                                 ref=build_ref, dirname=gd.dirname,
                                 remote=remote.get_push_url(), chatty=True)
+            bb.push_build_branches(push_cb=report_push)
 
             build_command.build([bb.root_repo_url,
                                  bb.root_ref,
diff --git a/morphlib/plugins/deploy_plugin.py b/morphlib/plugins/deploy_plugin.py
index 38c17bc2..99ca6fc3 100644
--- a/morphlib/plugins/deploy_plugin.py
+++ b/morphlib/plugins/deploy_plugin.py
@@ -322,27 +322,31 @@ class DeployPlugin(cliapp.Plugin):
         bb = morphlib.buildbranch.BuildBranch(sb, build_ref_prefix,
                                               push_temporary=False)
         with contextlib.closing(bb) as bb:
-
-            for gd, build_ref in bb.add_uncommitted_changes():
+            def report_add(gd, build_ref, changed):
                 self.app.status(msg='Adding uncommitted changes '\
                                     'in %(dirname)s to %(ref)s',
                                 dirname=gd.dirname, ref=build_ref, chatty=True)
+            bb.add_uncommitted_changes(add_cb=report_add)
 
-            for gd in bb.inject_build_refs(loader):
+            def report_inject(gd):
                 self.app.status(msg='Injecting temporary build refs '\
                                     'into morphologies in %(dirname)s',
                                 dirname=gd.dirname, chatty=True)
+            bb.inject_build_refs(loader, inject_cb=report_inject)
 
-            for gd, build_ref in bb.update_build_refs(name, email, build_uuid):
+            def report_commit(gd, build_ref):
                 self.app.status(msg='Committing changes in %(dirname)s '\
                                     'to %(ref)s',
                                 dirname=gd.dirname, ref=build_ref, chatty=True)
+            bb.update_build_refs(name, email, build_uuid,
+                                 commit_cb=report_commit)
 
-            for gd, build_ref, remote in bb.push_build_branches():
+            def report_push(gd, build_ref, remote, refspec):
                 self.app.status(msg='Pushing %(ref)s in %(dirname)s '\
                                     'to %(remote)s',
                                 ref=build_ref, dirname=gd.dirname,
                                 remote=remote.get_push_url(), chatty=True)
+            bb.push_build_branches(push_cb=report_push)
 
             # Create a tempdir for this deployment to work in
             deploy_tempdir = tempfile.mkdtemp(