workflow-tools: check branch roots have systems

It's rather easy to accidentally try to create a system branch of
the `morph` repository rather than the `morphs` repository.

This commit verifies that a checked out branch contains system
morphologies, otherwise it aborts and cleans up.

1 files changed, 25 insertions, 0 deletions

diff --git a/morphlib/plugins/branch_and_merge_new_plugin.py b/morphlib/plugins/branch_and_merge_new_plugin.py
index 5a33d47b..e09417d2 100644
--- a/morphlib/plugins/branch_and_merge_new_plugin.py
+++ b/morphlib/plugins/branch_and_merge_new_plugin.py
@@ -15,6 +15,7 @@
 
 
 import cliapp
+import glob
 import logging
 import os
 import shutil
@@ -22,6 +23,13 @@ import shutil
 import morphlib
 
 
+class BranchRootHasNoSystemsError(cliapp.AppException):
+    def __init__(self, repo, ref):
+        cliapp.AppException.__init__(
+            self, 'System branch root repository %s '
+                  'has no system morphologies at ref %s' % (repo, ref))
+
+
 class SimpleBranchAndMergePlugin(cliapp.Plugin):
 
     '''Add subcommands for handling workspaces and system branches.'''
@@ -131,6 +139,10 @@ class SimpleBranchAndMergePlugin(cliapp.Plugin):
 
             gd = sb.clone_cached_repo(
                 cached_repo, system_branch, system_branch)
+
+            if not self._checkout_has_systems(gd):
+                raise BranchRootHasNoSystemsError(root_url, system_branch)
+
             gd.update_submodules(self.app)
             gd.update_remotes()
         except BaseException as e:
@@ -202,6 +214,10 @@ class SimpleBranchAndMergePlugin(cliapp.Plugin):
             gd = sb.clone_cached_repo(cached_repo, system_branch, base_ref)
             gd.branch(system_branch, base_ref)
             gd.checkout(system_branch)
+
+            if not self._checkout_has_systems(gd):
+                raise BranchRootHasNoSystemsError(root_url, base_ref)
+
             gd.update_submodules(self.app)
             gd.update_remotes()
         except BaseException as e:
@@ -267,3 +283,12 @@ class SimpleBranchAndMergePlugin(cliapp.Plugin):
                 msg="WARNING: %(message)s",
                 message=str(e), error=True)
 
+    @staticmethod
+    def _checkout_has_systems(gd):
+        for filename in glob.iglob(os.path.join(gd.dirname, '*.morph')):
+            with open(filename) as mf:
+                morphology = morphlib.morph2.Morphology(mf.read())
+                if morphology['kind'] == 'system':
+                    return True
+        return False
+