morph merge: Handle merge conflicts more helpfully

Unless the error is in the system morphs repo, we carry on trying to merge
after errors and report all of the failures at the end.

1 files changed, 35 insertions, 9 deletions

diff --git a/morphlib/plugins/branch_and_merge_plugin.py b/morphlib/plugins/branch_and_merge_plugin.py
index 11df2dc3..af73ad76 100644
--- a/morphlib/plugins/branch_and_merge_plugin.py
+++ b/morphlib/plugins/branch_and_merge_plugin.py
@@ -699,10 +699,14 @@ class BranchAndMergePlugin(cliapp.Plugin):
 
         return old, new
 
-    def merge_repo(self, dirty_repos, from_branch_dir, from_repo, from_ref,
+    def merge_repo(self, dirty_repos, failed_repos,
+                   from_branch_dir, from_repo, from_ref,
                    to_branch_dir, to_repo, to_ref):
         '''Merge changes for a system branch in a specific repository'''
 
+        if to_repo in failed_repos:
+            return None
+
         from_repo_dir = self.find_repository(from_branch_dir, from_repo)
         to_repo_dir = self.checkout_repository(to_branch_dir, to_repo, to_ref)
 
@@ -721,10 +725,14 @@ class BranchAndMergePlugin(cliapp.Plugin):
         from_url = urlparse.urljoin('file://', from_repo_dir)
 
         status, output, error = self.app.runcmd_unchecked(
-            ['git', 'pull', '--no-commit', '--no-ff', from_url, from_ref],
-            cwd=to_repo_dir)
+            ['git', 'pull', '--quiet', '--no-commit', '--no-ff',
+             from_url, from_ref], cwd=to_repo_dir)
         if status != 0:
-            raise cliapp.AppException('merge conflict: %s' % (output))
+            self.app.output.write(
+                'Merge errors encountered merging into %s in repo %s:\n%s%s\n'
+                % (to_ref, to_repo, error, output))
+            failed_repos.add(to_repo)
+            return None
         return to_repo_dir
 
     def merge(self, args):
@@ -752,13 +760,17 @@ class BranchAndMergePlugin(cliapp.Plugin):
 
         def merge_chunk(old_ci, ci):
             self.merge_repo(
-                dirty_repos, from_branch_dir, old_ci['repo'], from_branch,
+                dirty_repo_dirs, failed_repos,
+                from_branch_dir, old_ci['repo'], from_branch,
                 to_branch_dir, ci['repo'], ci['ref'])
 
         def merge_stratum(old_si, si):
             to_repo_dir = self.merge_repo(
-                dirty_repos, from_branch_dir, old_si['repo'], from_branch,
+                dirty_repo_dirs, failed_repos,
+                from_branch_dir, old_si['repo'], from_branch,
                 to_branch_dir, si['repo'], si['ref'])
+            if to_repo_dir is None:
+                return
 
             old_stratum, stratum = self.load_morphology_pair(
                 to_repo_dir, old_si['ref'], si['morph'])
@@ -782,11 +794,18 @@ class BranchAndMergePlugin(cliapp.Plugin):
                 self.app.runcmd(['git', 'add', si['morph'] + '.morph'],
                                 cwd=to_repo_dir)
 
-        dirty_repos = set()
+        dirty_repo_dirs = set()
+        failed_repos = set()
 
         to_root_dir = self.merge_repo(
-            dirty_repos, from_branch_dir, root_repo, from_branch,
+            dirty_repo_dirs, failed_repos,
+            from_branch_dir, root_repo, from_branch,
             to_branch_dir, root_repo, to_branch)
+        if to_root_dir is None:
+            raise cliapp.AppException(
+                'Merging failed in %s: please manually merge %s into %s in '
+                'this repo and try again.' %
+                (root_repo, to_branch, from_branch))
 
         for f in glob.glob(os.path.join(to_root_dir, '*.morph')):
             name = os.path.basename(f)[:-len('.morph')]
@@ -815,7 +834,14 @@ class BranchAndMergePlugin(cliapp.Plugin):
                     self.save_morphology(to_root_dir, name, morphology)
                     self.app.runcmd(['git', 'add', f], cwd=to_root_dir)
 
-        for repo_dir in dirty_repos:
+        if len(failed_repos) > 0:
+            raise cliapp.AppException(
+                'merging errors were encountered in the following %s: %s\n\n'
+                'Please manually merge the target ref into %s in each case.' %
+                ('repository' if len(failed_repos) == 1 else 'repositories',
+                 ', '.join(failed_repos), from_branch))
+
+        for repo_dir in dirty_repo_dirs:
             # Repo will often turn out to not be dirty: if the changes we
             # merged only updated refs to the system branch, we will have
             # changed them back again so that the index will now be empty.