B&M: refactor branch-from-image

This changes the interface of branch-from-image to only take 1 parameter,
the name of the new system branch, as the root repository is loaded from
the metadata.

This was also what the previous version of branch-from-image did, but
that silently ignored the parameter.

Given there are not many users of branch-from-image, I felt it was a
reasonable change.

3 files changed, 108 insertions, 11 deletions

diff --git a/morphlib/plugins/branch_and_merge_new_plugin.py b/morphlib/plugins/branch_and_merge_new_plugin.py
index 7cd84898..809699eb 100644
--- a/morphlib/plugins/branch_and_merge_new_plugin.py
+++ b/morphlib/plugins/branch_and_merge_new_plugin.py
@@ -56,6 +56,15 @@ class SimpleBranchAndMergePlugin(cliapp.Plugin):
                                 arg_synopsis='-- COMMAND [ARGS...]')
         self.app.add_subcommand('status', self.status,
                                 arg_synopsis='')
+        self.app.add_subcommand('branch-from-image', self.branch_from_image,
+                                arg_synopsis='BRANCH')
+        group_branch = 'Branching Options'
+        self.app.settings.string(['metadata-dir'],
+                                  'Set metadata location for branch-from-image'
+                                  ' (default: /baserock)',
+                                  metavar='DIR',
+                                  default='/baserock',
+                                  group=group_branch)
 
     def disable(self):
         pass
@@ -790,3 +799,98 @@ class SimpleBranchAndMergePlugin(cliapp.Plugin):
 
         if not has_uncommitted_changes:
             self.app.output.write("\nNo repos have outstanding changes.\n")
+
+    def branch_from_image(self, args):
+        '''Produce a branch of an existing system image.
+
+        Given the metadata specified by --metadata-dir, create a new
+        branch then petrify it to the state of the commits at the time
+        the system was built.
+
+        If --metadata-dir is not specified, it defaults to your currently
+        running system.
+
+        '''
+        if len(args) != 1:
+            raise cliapp.AppException(
+                "branch-from-image needs exactly 1 argument "
+                "of the new system branch's name")
+        system_branch = args[0]
+        metadata_path = self.app.settings['metadata-dir']
+        alias_resolver = morphlib.repoaliasresolver.RepoAliasResolver(
+            self.app.settings['repo-alias'])
+
+        self._require_git_user_config()
+
+        ws = morphlib.workspace.open('.')
+
+        system, metadata = self._load_system_metadata(metadata_path)
+        resolved_refs = dict(self._resolve_refs_from_metadata(alias_resolver,
+                                                              metadata))
+        logging.debug('Resolved refs: %r' % resolved_refs)
+        base_ref = system['sha1']
+        # The previous version would fall back to deducing this from the repo
+        # url and the repo alias resolver, but this does not always work, and
+        # new systems always have repo-alias in the metadata
+        root_url = system['repo-alias']
+
+        lrc, rrc = morphlib.util.new_repo_caches(self.app)
+        cached_repo = lrc.get_updated_repo(root_url)
+
+
+        with self._initializing_system_branch(
+            ws, root_url, system_branch, cached_repo, base_ref) as (sb, gd):
+
+            # TODO: It's nasty to clone to a sha1 then create a branch
+            #       of that sha1 then check it out, a nicer API may be the
+            #       initial clone not checking out a branch at all, then
+            #       the user creates and checks out their own branches
+            gd.branch(system_branch, base_ref)
+            gd.checkout(system_branch)
+
+            loader = morphlib.morphloader.MorphologyLoader()
+            morphs = self._load_all_sysbranch_morphologies(sb, loader)
+
+            morphs.repoint_refs(sb.root_repository_url,
+                                sb.system_branch_name)
+
+            morphs.petrify_chunks(resolved_refs)
+
+            self._save_dirty_morphologies(loader, sb, morphs.morphologies)
+
+    @staticmethod
+    def _load_system_metadata(path):
+        '''Load all metadata in `path` corresponding to a single System.
+        '''
+
+        smd = morphlib.systemmetadatadir.SystemMetadataDir(path)
+        metadata = smd.values()
+        systems = [md for md in metadata
+                   if 'kind' in md and md['kind'] == 'system']
+
+        if not systems:
+            raise cliapp.AppException(
+                'Metadata directory does not contain any systems.')
+        if len(systems) > 1:
+            raise cliapp.AppException(
+                'Metadata directory contains multiple systems.')
+        system_metadatum = systems[0]
+    
+        metadata_cache_id_lookup = dict((md['cache-key'], md)
+                                        for md in metadata)
+
+        return system_metadatum, metadata_cache_id_lookup
+
+    @staticmethod
+    def _resolve_refs_from_metadata(alias_resolver, metadata):
+        '''Pre-resolve a set of refs from existing metadata.
+
+        Given the metadata, generate a mapping of all the (repo, ref)
+        pairs defined in the metadata and the commit id they resolved to.
+
+        '''
+        for md in metadata.itervalues():
+            repourls = set((md['repo-alias'], md['repo']))
+            repourls.update(alias_resolver.aliases_from_url(md['repo']))
+            for repourl in repourls:
+                yield ((repourl, md['original_ref']), md['sha1'])
diff --git a/morphlib/plugins/branch_and_merge_plugin.py b/morphlib/plugins/branch_and_merge_plugin.py
index 37d5e40c..2f8560d0 100644
--- a/morphlib/plugins/branch_and_merge_plugin.py
+++ b/morphlib/plugins/branch_and_merge_plugin.py
@@ -68,15 +68,9 @@ class BranchAndMergePlugin(cliapp.Plugin):
         self.app.add_subcommand('build', self.build,
                                 arg_synopsis='SYSTEM')
         self.app.add_subcommand('old-status', self.status)
-        self.app.add_subcommand('branch-from-image', self.branch_from_image,
-                                 arg_synopsis='REPO BRANCH')
-        group_branch = 'Branching Options'
-        self.app.settings.string(['metadata-dir'],
-                                  'Set metadata location for branch-from-image'
-                                  ' (default: /baserock)',
-                                  metavar='DIR',
-                                  default='/baserock',
-                                  group=group_branch)
+        self.app.add_subcommand('old-branch-from-image',
+                                self.branch_from_image,
+                                arg_synopsis='REPO BRANCH')
 
         # Advanced commands
         self.app.add_subcommand('old-foreach', self.foreach,
diff --git a/tests.as-root/branch-from-image-works.script b/tests.as-root/branch-from-image-works.script
index 9f82f629..942301e8 100755
--- a/tests.as-root/branch-from-image-works.script
+++ b/tests.as-root/branch-from-image-works.script
@@ -48,8 +48,7 @@ git commit --quiet -m 'Make hello say goodbye'
 workspace="$DATADIR/workspace"
 "$SRCDIR/scripts/test-morph" init "$workspace"
 cd "$workspace"
-"$SRCDIR/scripts/test-morph" branch-from-image \
-                             test:morphs mybranch \
+"$SRCDIR/scripts/test-morph" branch-from-image  mybranch \
                              --metadata-dir="$extracted/baserock"
 cd mybranch/test:morphs
 grep -qFe "$hello_chunk_commit" hello-stratum.morph