Merge branch 'samthursfield/complex-merges-2' of git://roadtrain.codethink.co.uk/baserock/morph

16 files changed, 444 insertions, 69 deletions

diff --git a/morphlib/git.py b/morphlib/git.py
index 9ab98ad0..5862ef9b 100644
--- a/morphlib/git.py
+++ b/morphlib/git.py
@@ -196,6 +196,17 @@ def checkout_ref(runcmd, gitdir, ref):
     '''Checks out a specific ref/SHA1 in a git working tree.'''
     runcmd(['git', 'checkout', ref], cwd=gitdir)
 
+
+def index_has_changes(runcmd, gitdir):
+    '''Returns True if there are no staged changes to commit'''
+    try:
+        runcmd(['git', 'diff-index', '--cached', '--quiet',
+                '--ignore-submodules', 'HEAD'], cwd=gitdir)
+    except cliapp.AppException:
+        return True
+    return False
+
+
 def reset_workdir(runcmd, gitdir):
     '''Removes any differences between the current commit '''
     '''and the status of the working directory'''
diff --git a/morphlib/plugins/branch_and_merge_plugin.py b/morphlib/plugins/branch_and_merge_plugin.py
index 82d83a58..75935b72 100644
--- a/morphlib/plugins/branch_and_merge_plugin.py
+++ b/morphlib/plugins/branch_and_merge_plugin.py
@@ -475,27 +475,34 @@ class BranchAndMergePlugin(cliapp.Plugin):
         branch_root = self.get_branch_config(branch_dir, 'branch.root')
         self.app.output.write('%s\n' % branch_root)
 
-    def make_repository_available(self, system_branch, branch_dir, repo, ref):
-        existing_repo = self.find_repository(branch_dir, repo)
-        if existing_repo:
-            # Reuse the existing clone and its system branch.
-            self.app.runcmd(['git', 'checkout', system_branch],
-                            cwd=existing_repo)
-            return existing_repo
-        else:
-            # Clone repo and create the system branch in the cloned repo.
+    def checkout_repository(self, branch_dir, repo, ref, parent_ref=None):
+        '''Make a chunk or stratum repository available for a system branch
+
+        We ensure the 'system_branch' ref within 'repo' is checked out,
+        creating it from 'parent_ref' if required.
+
+        The function aims for permissiveness, so users can try to fix any
+        weirdness they have caused in the repos with another call to 'morph
+        edit'.
+
+        '''
+
+        parent_ref = parent_ref or ref
+
+        repo_dir = self.find_repository(branch_dir, repo)
+        if repo_dir is None:
             repo_url = self.resolve_reponame(repo)
             repo_dir = os.path.join(branch_dir, self.convert_uri_to_path(repo))
-            self.clone_to_directory(repo_dir, repo, ref)
-            try:
-                self.log_change(repo, 'branch "%s" created from "%s"' %
-                                (system_branch, ref))
-                self.app.runcmd(['git', 'checkout', '-b', system_branch],
-                                cwd=repo_dir)
-            except:
-                self.app.runcmd(['git', 'checkout', system_branch],
-                                cwd=repo_dir)
-            return repo_dir
+            self.clone_to_directory(repo_dir, repo, parent_ref)
+
+        if self.resolve_ref(repo_dir, ref) is None:
+            self.log_change(repo, 'branch "%s" created from "%s"' %
+                            (ref, parent_ref))
+            self.app.runcmd(['git', 'checkout', '-b', ref], cwd=repo_dir)
+        else:
+            # git copes even if the system_branch ref is already checked out
+            self.app.runcmd(['git', 'checkout', ref], cwd=repo_dir)
+        return repo_dir
 
     def edit(self, args):
         '''Edit a component in a system branch.'''
@@ -523,8 +530,9 @@ class BranchAndMergePlugin(cliapp.Plugin):
                                      stratum_name, collection='strata')
 
         # Make the stratum repository and the ref available locally.
-        stratum_repo_dir = self.make_repository_available(
-            system_branch, branch_dir, stratum['repo'], stratum['ref'])
+        stratum_repo_dir = self.checkout_repository(
+            branch_dir, stratum['repo'], system_branch,
+            parent_ref=stratum['ref'])
 
         # Check if we need to change anything at all.
         if stratum['ref'] != system_branch:
@@ -560,8 +568,9 @@ class BranchAndMergePlugin(cliapp.Plugin):
                                        chunk_name, collection='chunks')
 
             # Make the chunk repository and the ref available locally.
-            chunk_repo_dir = self.make_repository_available(
-                    system_branch, branch_dir, chunk['repo'], chunk['ref'])
+            chunk_repo_dir = self.checkout_repository(
+                    branch_dir, chunk['repo'], system_branch,
+                    parent_ref=chunk['ref'])
 
             # Check if we need to update anything at all.
             if chunk['ref'] != system_branch:
@@ -577,13 +586,38 @@ class BranchAndMergePlugin(cliapp.Plugin):
         self.print_changelog('The following changes were made but have not '
                              'been comitted')
 
+    def load_morphology_pair(self, repo_dir, ref, name):
+        '''Load two versions of a morphology and check for major conflicts
+
+        Returns the version at 'ref' (if it exists) and the on-disk version.
+
+        '''
+
+        new = self.load_morphology(repo_dir, name)
+        try:
+            old = self.load_morphology(repo_dir, name, ref=ref)
+        except cliapp.AppException as e:
+            return None, new
+
+        if old['name'] != new['name']:
+            # We should enforce this in validation during load_morphology()
+            # rather than having to check it here
+            raise cliapp.AppException(
+                'merge confict: "name" of morphology %s (name should '
+                'always match filename)' % name)
+        if old['kind'] != new['kind']:
+            raise cliapp.AppException(
+                'merge conflict: "kind" of morphology %s' % name)
+
+        return old, new
+
     def merge_repo(self, name, from_dir, from_branch, to_dir, to_branch,
                    commit = False):
         '''Merge changes for a system branch in a specific repository'''
 
         if self.get_uncommitted_changes(from_dir) != []:
             raise cliapp.AppException('repository %s has uncommitted '
-                                      'changes', name)
+                                      'changes' % from_dir)
         # repo must be made into a URL to avoid ':' in pathnames confusing git
         from_url = urlparse.urljoin('file://', from_dir)
         self.app.runcmd(['git', 'pull', '--no-commit', '--no-ff', from_url,
@@ -615,54 +649,87 @@ class BranchAndMergePlugin(cliapp.Plugin):
                                       'repository : %s vs %s' %
                                       (root_repo, other_root_repo))
 
-        def _merge_chunk(ci):
-            from_repo = self.find_repository(from_branch_dir, ci['repo'])
-            to_repo = self.make_repository_available(
-                to_branch, to_branch_dir, ci['repo'], to_branch)
+        def merge_chunk(old_ci, ci):
+            from_repo = self.find_repository(from_branch_dir, old_ci['repo'])
+            to_repo = self.checkout_repository(
+                to_branch_dir, ci['repo'], ci['ref'])
             self.merge_repo(ci['repo'], from_repo, from_branch,
-                            to_repo, to_branch, commit=True)
+                            to_repo, ci['ref'], commit=True)
 
-        def _merge_stratum(si):
-            if si['repo'] == root_repo:
-                to_repo = to_root_dir
-            else:
-                from_repo = self.find_repository(from_branch_dir, si['repo'])
-                to_repo = self.make_repository_available(
-                    to_branch, to_branch_dir, si['repo'], to_branch)
-                # We will do a merge commit in this repo later on
-                self.merge_repo(si['repo'], from_repo, from_branch,
-                                to_repo, to_branch, commit=False)
-                morphs_repo_list.add(to_repo)
+        def merge_stratum(old_si, si):
+            from_repo = self.find_repository(from_branch_dir, old_si['repo'])
+            to_repo = self.checkout_repository(
+                to_branch_dir, si['repo'], si['ref'])
 
-            stratum = self.load_morphology(to_repo, si['morph'])
-            for ci in stratum['chunks']:
-                if ci['ref'] == from_branch:
-                    _merge_chunk(ci)
-                    ci['ref'] = to_branch
-            self.save_morphology(to_repo, si['morph'], stratum)
+            if to_repo not in dirty_repos:
+                self.merge_repo(si['repo'], from_repo, from_branch,
+                                to_repo, si['ref'], commit=False)
+                dirty_repos.add(to_repo)
+            old_stratum, stratum = self.load_morphology_pair(
+                to_repo, old_si['ref'], si['morph'])
+
+            changed = False
+            edited_chunks = [ci for ci in stratum['chunks']
+                             if ci['ref'] == from_branch]
+            for ci in edited_chunks:
+                for old_ci in old_stratum['chunks']:
+                    if old_ci['repo'] == ci['repo']:
+                        break
+                else:
+                    raise cliapp.AppException(
+                        'chunk %s was added within this branch and '
+                        'subsequently edited. This is not yet supported: '
+                        'refusing to merge.' % ci['name'])
+                changed = True
+                ci['ref'] = old_ci['ref']
+                merge_chunk(old_ci, ci)
+            if changed:
+                self.save_morphology(to_repo, si['morph'], stratum)
+                self.app.runcmd(['git', 'add', si['morph'] + '.morph'],
+                                cwd=to_repo)
 
         from_root_dir = self.find_repository(from_branch_dir, root_repo)
         to_root_dir = self.find_repository(to_branch_dir, root_repo)
         self.app.runcmd(['git', 'checkout', to_branch], cwd=to_root_dir)
         self.merge_repo(root_repo, from_root_dir, from_branch,
                         to_root_dir, to_branch, commit=False)
-        morphs_repo_list = set([to_root_dir])
+        dirty_repos = set([to_root_dir])
 
         for f in glob.glob(os.path.join(to_root_dir, '*.morph')):
-            name = f[:-len('.morph')]
-            morphology = self.load_morphology(to_root_dir, name)
+            name = os.path.basename(f)[:-len('.morph')]
+            old_morphology, morphology = self.load_morphology_pair(
+                to_root_dir, to_branch, name)
 
             if morphology['kind'] == 'system':
-                for si in morphology['strata']:
-                    if si['ref'] == from_branch:
-                        _merge_stratum(si)
-                    si['ref'] = to_branch
-                self.save_morphology(to_root_dir, name, morphology)
-
-        for repo in morphs_repo_list:
-            msg = "Merge system branch '%s'" % from_branch
-            self.app.runcmd(['git', 'commit', '--all', '--message=%s' % msg],
-                            cwd=repo)
+                changed = False
+                edited_strata = [si for si in morphology['strata']
+                                 if si['ref'] == from_branch]
+                for si in edited_strata:
+                    for old_si in old_morphology['strata']:
+                        # We make no attempt at rename / move detection
+                        if old_si['morph'] == si['morph'] \
+                                and old_si['repo'] == si['repo']:
+                            break
+                    else:
+                        raise cliapp.AppException(
+                            'stratum %s was added within this branch and '
+                            'subsequently edited. This is not yet supported: '
+                            'refusing to merge.' % si['morph'])
+                    changed = True
+                    si['ref'] = old_si['ref']
+                    merge_stratum(old_si, si)
+                if changed:
+                    self.save_morphology(to_root_dir, name, morphology)
+                    self.app.runcmd(['git', 'add', f], cwd=to_root_dir)
+
+        for repo_dir in dirty_repos:
+            # 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.
+            if morphlib.git.index_has_changes(self.app.runcmd, repo_dir):
+                msg = "Merge system branch '%s'" % from_branch
+                self.app.runcmd(['git', 'commit', '--all', '-m%s' % msg],
+                                cwd=repo_dir)
 
     def build(self, args):
         if len(args) != 1:
diff --git a/tests.branching/merge-handles-unmergable-cases.exit b/tests.branching/merge-handles-unmergable-cases.exit
new file mode 100644
index 00000000..d00491fd
--- /dev/null
+++ b/tests.branching/merge-handles-unmergable-cases.exit
@@ -0,0 +1 @@
+1
diff --git a/tests.branching/merge-handles-unmergable-cases.script b/tests.branching/merge-handles-unmergable-cases.script
new file mode 100755
index 00000000..fd7f1478
--- /dev/null
+++ b/tests.branching/merge-handles-unmergable-cases.script
@@ -0,0 +1,30 @@
+#!/bin/sh
+# Copyright (C) 2012  Codethink Limited
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+# Things that "morph merge" isn't expected to handle (but shouldn't crash)
+
+set -eu
+
+cd "$DATADIR/workspace"
+"$SRCDIR/scripts/test-morph" init
+"$SRCDIR/scripts/test-morph" checkout baserock:morphs master
+"$SRCDIR/scripts/test-morph" branch baserock:morphs test/unmergable
+
+cd "$DATADIR/workspace/test/unmergable/baserock:morphs"
+sed -ie 's/"kind": "stratum"/"kind": "chunk"/' hello-stratum.morph
+git commit --quiet --all -m "Unmergeable because kind has changed"
+cd "$DATADIR/workspace/master/baserock:morphs"
+"$SRCDIR/scripts/test-morph" merge test/unmergable
diff --git a/tests.branching/merge-handles-unmergable-cases.stderr b/tests.branching/merge-handles-unmergable-cases.stderr
new file mode 100644
index 00000000..513db2b8
--- /dev/null
+++ b/tests.branching/merge-handles-unmergable-cases.stderr
@@ -0,0 +1 @@
+ERROR: merge conflict: "kind" of morphology hello-stratum
diff --git a/tests.branching/merge-not-to-master.script b/tests.branching/merge-not-to-master.script
new file mode 100755
index 00000000..3758ce3e
--- /dev/null
+++ b/tests.branching/merge-not-to-master.script
@@ -0,0 +1,69 @@
+#!/bin/sh
+# Copyright (C) 2012  Codethink Limited
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+# Check that "morph merge" merges a system branch into a newly created
+# system branch
+
+set -eu
+
+cd "$DATADIR/workspace"
+"$SRCDIR/scripts/test-morph" init
+
+# Create stable branch to merge TO
+"$SRCDIR/scripts/test-morph" branch baserock:morphs test/stable
+cd test/stable/baserock:morphs
+git push --quiet origin test/stable
+
+# Create feature branch to merge FROM
+"$SRCDIR/scripts/test-morph" branch baserock:morphs test/feature test/stable
+cd "$DATADIR/workspace/test/feature"
+
+# Edit hello in FROM
+"$SRCDIR/scripts/test-morph" edit hello-system hello-stratum hello
+cd baserock:hello
+touch newfile.txt
+git add newfile.txt
+git commit -m foo --quiet
+
+# Commit in morphs repo
+# FIXME: this should become unnecessary since only the refs have
+# changed.
+cd ../baserock:morphs
+git commit --all --quiet -m "Update morph refs for test/feature"
+
+# Merge changes back to test/stable
+cd "$DATADIR/workspace"
+cd test/stable
+"$SRCDIR/scripts/test-morph" merge test/feature
+
+# Check results: changes to 'hello' should have been merged back to
+# test/stable.
+cd baserock:hello
+[ -e newfile.txt ]
+
+# Make sure all changes are committed and to the correct branch ('hello'
+# was built from 'master' before branching, so the changes should be
+# merged back to 'master').
+git status --short
+[ $(git rev-parse master) = $(git rev-parse HEAD) ]
+
+# Changes here should be on test/stable.
+cd ../baserock:morphs
+git status --short
+[ $(git rev-parse test/stable) = $(git rev-parse HEAD) ]
+
+# Make sure all refs to the merged branch have gone.
+! grep "\"ref\": \"test/feature\"" *.morph
diff --git a/tests.branching/merge-with-chunk-renamed.script b/tests.branching/merge-with-chunk-renamed.script
new file mode 100755
index 00000000..1ca2ee48
--- /dev/null
+++ b/tests.branching/merge-with-chunk-renamed.script
@@ -0,0 +1,56 @@
+#!/bin/sh
+# Copyright (C) 2012  Codethink Limited
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+# "morph merge" should pull changes from a chunk even if its name was changed
+# in the branch
+
+set -eu
+
+# Create system branch.
+cd "$DATADIR/workspace"
+"$SRCDIR/scripts/test-morph" init
+"$SRCDIR/scripts/test-morph" branch baserock:morphs baserock/newbranch
+
+# Rename the chunk, and then commit a seperate change
+"$SRCDIR/scripts/test-morph" edit hello-system hello-stratum hello
+cd baserock/newbranch/baserock:hello
+
+cat hello.morph | sed -e 's/"name": "hello"/"name": "goodbye"/' > goodbye.morph
+git rm -q hello.morph
+git add goodbye.morph
+git commit -m "Rename chunk" --quiet
+
+touch newfile.txt
+git add newfile.txt
+git commit -m "Add new file" --quiet
+
+# Update stratum to point at the renamed chunk
+cd ../baserock:morphs
+sed -ie 's/"name": "hello"/"name": "goodbye"/' hello-stratum.morph
+git commit --all --quiet -m "Update morph refs for baserock/newbranch"
+
+# Merge changes back to master
+cd "$DATADIR/workspace"
+"$SRCDIR/scripts/test-morph" checkout baserock:morphs master
+cd master
+"$SRCDIR/scripts/test-morph" merge baserock/newbranch
+
+# Morph should have realised that 'goodbye' is not a new chunk,
+# and pulled in the changes from 'hello' in the old branch
+cd baserock:hello
+[ ! -e hello.morph ]
+[ -e goodbye.morph ]
+[ -e newfile.txt ]
diff --git a/tests.branching/merge-with-chunk-repo-moved.exit b/tests.branching/merge-with-chunk-repo-moved.exit
new file mode 100644
index 00000000..d00491fd
--- /dev/null
+++ b/tests.branching/merge-with-chunk-repo-moved.exit
@@ -0,0 +1 @@
+1
diff --git a/tests.branching/merge-with-chunk-repo-moved.script b/tests.branching/merge-with-chunk-repo-moved.script
new file mode 100755
index 00000000..c67ccc6d
--- /dev/null
+++ b/tests.branching/merge-with-chunk-repo-moved.script
@@ -0,0 +1,53 @@
+#!/bin/sh
+# Copyright (C) 2012  Codethink Limited
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+# "morph merge" should detect changes in a repo that was added as part of the
+# branch and warn the user that the changes will not be merged automatically
+
+set -eu
+
+# Create system branch.
+cd "$DATADIR/workspace"
+"$SRCDIR/scripts/test-morph" init
+"$SRCDIR/scripts/test-morph" branch baserock:morphs baserock/newbranch
+
+"$SRCDIR/scripts/test-morph" edit hello-system hello-stratum hello
+
+# Chunk moves to a new location (we manually update the ref back to master
+# here, so 'morph edit' can create a system branch in the new repo from it).
+git clone -q "$DATADIR/hello" "$DATADIR/hello-lorried"
+cd "$DATADIR/workspace/baserock/newbranch/baserock:morphs"
+sed -e 's/"repo": "baserock:hello"/"repo": "baserock:hello-lorried"/' \
+    -e 's/"ref": "baserock\/newbranch"/"ref": "master"/' \
+    -i hello-stratum.morph
+git commit -q --all -m "'hello' repository has moved"
+
+# Now we further edit the chunk, just for fun.
+"$SRCDIR/scripts/test-morph" edit hello-system hello-stratum hello
+cd "$DATADIR/workspace/baserock/newbranch/baserock:hello-lorried"
+touch newfile.txt
+git add newfile.txt
+git commit -m "Add new file" --quiet
+
+cd "$DATADIR/workspace/baserock/newbranch/baserock:morphs"
+git commit -q --all -m "Update system branch refs"
+
+# Try to merge changes back to master (should fail, because we don't support
+# adding chunks inside branches yet).
+cd "$DATADIR/workspace"
+"$SRCDIR/scripts/test-morph" checkout baserock:morphs master
+cd master
+"$SRCDIR/scripts/test-morph" merge baserock/newbranch
diff --git a/tests.branching/merge-with-chunk-repo-moved.stderr b/tests.branching/merge-with-chunk-repo-moved.stderr
new file mode 100644
index 00000000..95fe61e6
--- /dev/null
+++ b/tests.branching/merge-with-chunk-repo-moved.stderr
@@ -0,0 +1 @@
+ERROR: chunk hello was added within this branch and subsequently edited. This is not yet supported: refusing to merge.
diff --git a/tests.branching/merge-with-stratum-renamed.exit b/tests.branching/merge-with-stratum-renamed.exit
new file mode 100644
index 00000000..d00491fd
--- /dev/null
+++ b/tests.branching/merge-with-stratum-renamed.exit
@@ -0,0 +1 @@
+1
diff --git a/tests.branching/merge-with-stratum-renamed.script b/tests.branching/merge-with-stratum-renamed.script
new file mode 100755
index 00000000..8df2cd18
--- /dev/null
+++ b/tests.branching/merge-with-stratum-renamed.script
@@ -0,0 +1,51 @@
+#!/bin/sh
+# Copyright (C) 2012  Codethink Limited
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+# "morph merge" should deal with stratum renames; currently it doesn't deal
+# very well, but at least we don't crash.
+
+set -eu
+
+# Create system branch.
+cd "$DATADIR/workspace"
+"$SRCDIR/scripts/test-morph" init
+"$SRCDIR/scripts/test-morph" branch baserock:morphs baserock/newbranch
+
+# The user may 'morph edit hello-system hello-stratum hello' and commit here:
+# we currently silently ignore her changes on merge, because we don't
+# associate hello-stratum and goodbye-stratum at all.
+
+# Rename the stratum
+"$SRCDIR/scripts/test-morph" edit hello-system hello-stratum
+cd baserock/newbranch/baserock:morphs
+
+sed -e 's/"morph": "hello-stratum"/"morph": "goodbye-stratum"/'\
+    -i hello-system.morph
+sed -e 's/"name": "hello-stratum"/"name": "goodbye-stratum"/' \
+    hello-stratum.morph > goodbye-stratum.morph
+git rm -q hello-stratum.morph
+git add goodbye-stratum.morph
+git commit -q --all -m "Rename hello-stratum to goodbye-stratum"
+
+# The user may 'morph edit hello-system goodbye-stratum hello' and commit
+# here, too: same problem.
+
+# Merge changes back to master (this should fail, because we don't support
+# adding strata inside branches yet).
+cd "$DATADIR/workspace"
+"$SRCDIR/scripts/test-morph" checkout baserock:morphs master
+cd master
+"$SRCDIR/scripts/test-morph" merge baserock/newbranch
diff --git a/tests.branching/merge-with-stratum-renamed.stderr b/tests.branching/merge-with-stratum-renamed.stderr
new file mode 100644
index 00000000..ad144f93
--- /dev/null
+++ b/tests.branching/merge-with-stratum-renamed.stderr
@@ -0,0 +1 @@
+ERROR: stratum goodbye-stratum was added within this branch and subsequently edited. This is not yet supported: refusing to merge.
diff --git a/tests.branching/merge.script b/tests.branching/merge.script
index d8a28cb3..21a30116 100755
--- a/tests.branching/merge.script
+++ b/tests.branching/merge.script
@@ -49,6 +49,8 @@ git status --short # make sure all changes are committed
 cd ../baserock:morphs
 ! grep "\"ref\": \"baserock/newbranch\"" *.morph
 
+# The only change here was the branch refs, which have now been
+# changed back - so there should not be any new commits.
 echo "Commit message for baserock:morphs"
 git cat-file commit HEAD | tail -n 1
 
diff --git a/tests.branching/merge.stdout b/tests.branching/merge.stdout
index e5127734..6806f75a 100644
--- a/tests.branching/merge.stdout
+++ b/tests.branching/merge.stdout
@@ -1,5 +1,5 @@
 Commit message for baserock:morphs
-Merge system branch 'baserock/newbranch'
+initial
 
 Commit message for baserock:hello
 Merge system branch 'baserock/newbranch'
diff --git a/tests.branching/workflow-separate-stratum-repos.script b/tests.branching/workflow-separate-stratum-repos.script
index 3d0f6529..06c4f3b8 100755
--- a/tests.branching/workflow-separate-stratum-repos.script
+++ b/tests.branching/workflow-separate-stratum-repos.script
@@ -63,7 +63,6 @@ cat <<EOF > "$1/$2.morph"
 EOF
 }
 
-
 # Create two more strata outside the baserock:morphs repository
 
 EXTERNAL_STRATA_REPO="$DATADIR/external-strata"
@@ -84,14 +83,22 @@ git commit --quiet -m "Initial commit"
 create_chunk "$DATADIR/stratum2-hello" "hello"
 create_chunk "$DATADIR/stratum3-hello" "hello"
 
-# Update hello-system to include them
+# Update hello-system to include them ... using a system branch! Since the
+# strata refs are 'master' not 'me/add-external-strata' this does not cause
+# problems with merging.
 
-cd "$DATADIR/morphs"
-cat <<EOF > "$DATADIR/morphs/hello-system.morph"
+cd "$DATADIR/workspace"
+"$SRCDIR/scripts/test-morph" init
+"$SRCDIR/scripts/test-morph" branch baserock:morphs me/add-external-strata
+
+cd "$DATADIR/workspace/me/add-external-strata/baserock:morphs"
+
+cat <<EOF > "hello-system.morph"
 {
     "name": "hello-system",
     "kind": "system",
     "system-kind": "syslinux-disk",
+    "arch": "x86_64",
     "disk-size": "1G",
     "strata": [
         {
@@ -114,14 +121,26 @@ cat <<EOF > "$DATADIR/morphs/hello-system.morph"
 EOF
 git commit --quiet --all -m "Add two more external strata"
 
-# Now try to branch and merge the system
-# FIXME: we should try and build it, too
+# Merge to master
+cd "$DATADIR/workspace"
+"$SRCDIR/scripts/test-morph" checkout baserock:morphs master
+cd master/baserock:morphs
+"$SRCDIR/scripts/test-morph" merge me/add-external-strata
 
+# In reality the user would do: 'git push origin master' here,
+# but since our remote repo is non-bare we must cheat a bit.
+# We should consider a separate fixture for the workflow tests.
+cd "$DATADIR/morphs"
+git pull -q \
+    "file://$DATADIR/workspace/master/baserock:morphs" master
+
+# Now make another change to the system
+# FIXME: we should try and build it, too
 cd "$DATADIR/workspace"
-"$SRCDIR/scripts/test-morph" init
 "$SRCDIR/scripts/test-morph" branch baserock:morphs me/readme-fixes
 
 # Edit one chunk
+cd "me/readme-fixes"
 "$SRCDIR/scripts/test-morph" edit hello-system stratum2 hello
 cd "$DATADIR/workspace/me/readme-fixes/baserock:stratum2-hello"
 echo > README yoyoyo
@@ -135,7 +154,7 @@ echo > README yoyoyo
 git add README
 git commit -m "Fix README in hello" --quiet
 
-# Update the morphologies repos
+# Update the morphology repos
 cd ../baserock:external-strata
 git commit --quiet --all -m "Commit changes for system branch"
 
@@ -144,6 +163,17 @@ git commit --quiet --all -m "Commit changes for system branch"
 
 # Merge our system branch into master
 cd "$DATADIR/workspace"
-"$SRCDIR/scripts/test-morph" checkout baserock:morphs master
 cd master
 "$SRCDIR/scripts/test-morph" merge me/readme-fixes
+
+# Check the changes have appeared
+cd baserock:morphs
+[ $(git rev-parse HEAD) = $(git rev-parse master) ]
+
+cd ../baserock:stratum2-hello
+[ -e README ]
+[ $(git rev-parse HEAD) = $(git rev-parse master) ]
+
+cd ../baserock:stratum3-hello
+[ -e README ]
+[ $(git rev-parse HEAD) = $(git rev-parse master) ]