Make branch commands work with null refs

5 files changed, 106 insertions, 4 deletions

diff --git a/morphlib/morphset.py b/morphlib/morphset.py
index 3c07d58e..9ef1e804 100644
--- a/morphlib/morphset.py
+++ b/morphlib/morphset.py
@@ -95,9 +95,11 @@ class MorphologySet(object):
 
         repo_url, ref, morph = self._find_spec(
             system_morph['strata'], stratum_name)
-        if repo_url is None:
+        if (repo_url, ref, morph) == (None, None, None):
             raise StratumNotInSystemError(system_morph['name'], stratum_name)
-        m = self._get_morphology(repo_url, ref, '%s.morph' % morph)
+        m = self._get_morphology(repo_url or system_morph.repo_url,
+                                 ref or system_morph.ref,
+                                 '%s.morph' % morph)
         if m is None:
             raise StratumNotInSetError(stratum_name)
         return m
@@ -118,7 +120,7 @@ class MorphologySet(object):
 
         repo_url, ref, morph = self._find_spec(
             stratum_morph['chunks'], chunk_name)
-        if repo_url is None:
+        if (repo_url, ref, morph) == (None, None, None):
             raise ChunkNotInStratumError(stratum_morph['name'], chunk_name)
         return repo_url, ref, morph
 
diff --git a/morphlib/plugins/branch_and_merge_new_plugin.py b/morphlib/plugins/branch_and_merge_new_plugin.py
index 39552ef0..edda7d9c 100644
--- a/morphlib/plugins/branch_and_merge_new_plugin.py
+++ b/morphlib/plugins/branch_and_merge_new_plugin.py
@@ -266,7 +266,9 @@ class SimpleBranchAndMergePlugin(cliapp.Plugin):
         # of triplets (repo url, ref, filename).
 
         return [
-            (spec['repo'], spec['ref'], '%s.morph' % spec['morph'])
+            (spec['repo'] or morph.repo_url,
+             spec['ref'] or morph.ref,
+             '%s.morph' % spec['morph'])
             for spec in specs
         ]
 
@@ -679,6 +681,9 @@ class SimpleBranchAndMergePlugin(cliapp.Plugin):
         #TODO: Stop using app.resolve_ref
         def resolve_refs(morphs):
             for repo, ref in morphs.list_refs():
+                # You can't resolve null refs, so don't attempt to.
+                if repo is None or ref is None:
+                    continue
                 # TODO: Handle refs that are only in workspace in general
                 if (repo == sb.root_repository_url
                     and ref == sb.system_branch_name):
diff --git a/yarns/branches-workspaces.yarn b/yarns/branches-workspaces.yarn
index 5273f396..f523ebcd 100644
--- a/yarns/branches-workspaces.yarn
+++ b/yarns/branches-workspaces.yarn
@@ -290,3 +290,65 @@ Creating a tag twice should fail.
     WHEN        attempting to tag system branch foo as test123
     THEN        morph failed
 
+Working with null repositories and refs
+---------------------------------------
+
+It is convenient to not explicitly name the repository and branch of
+a stratum morphology, instead assuming it is the same as the current
+morphology.
+
+These can be checked out like normal system branches.
+
+    SCENARIO    check out an existing system branch with null refs
+    GIVEN       a workspace
+    AND         a git server
+    AND         null refs for local strata
+    WHEN        checking out the master system branch
+    THEN        the system branch master is checked out
+
+Likewise we can also create new system branches from these, and we
+wouldn't need to worry about changing the system branch ref.
+
+
+    SCENARIO    branch off a system branch with null refs
+    GIVEN       a workspace
+    AND         a git server
+    AND         null refs for local strata
+    WHEN        creating system branch foo
+    THEN        the system branch foo is checked out
+
+When we edit a morphology with null refs, they stay null.
+
+    SCENARIO    editing with null refs
+    GIVEN       a workspace
+    AND         a git server
+    AND         null refs for local strata
+
+When creating the branch, the refs remain null.
+
+    WHEN        creating system branch foo
+    THEN        in branch foo, system test-system refs test-stratum in None
+
+After editing the stratum they remain null.
+
+    WHEN    editing stratum test-stratum in system test-system in branch foo
+    THEN    in branch foo, system test-system refs test-stratum in None
+
+Refs to chunks are still altered as usual
+
+    WHEN editing chunk test-chunk in test-stratum in test-system in branch foo
+    THEN in branch foo, system test-system refs test-stratum in None
+    AND  in branch foo, stratum test-stratum refs test-chunk in foo
+    AND  edited chunk test:test-chunk has git branch foo
+
+Petrifying also leaves null refs unmolested
+
+    SCENARIO    morph petrifies null refs
+    GIVEN       a workspace
+    AND         a git server
+    AND         null refs for local strata
+    WHEN        creating system branch foo
+    AND         pushing system branch foo to git server
+    AND         remembering all refs in foo
+    AND         petrifying foo
+    THEN        in branch foo, system test-system refs test-stratum in None
diff --git a/yarns/implementations.yarn b/yarns/implementations.yarn
index cfb744f7..e35e4219 100644
--- a/yarns/implementations.yarn
+++ b/yarns/implementations.yarn
@@ -114,6 +114,18 @@ another to hold a chunk.
     repo-alias = test=file://$DATADIR/gits/%s#file://$DATADIR/gits/%s
     EOF
 
+Morphologies need to support having a null ref, which means look for the
+stratum in the same repository and ref. Testing this requires different
+morphologies.
+
+    IMPLEMENTS GIVEN null refs for local strata
+    nullify_local_refs test:morphs master \
+        "$DATADIR/gits/morphs/test-system.morph" \
+        "$DATADIR/gits/morphs/test-stratum.morph"
+    run_in "$DATADIR/gits/morphs" git add .
+    run_in "$DATADIR/gits/morphs" git commit -m "Use null refs."
+
+
 Implementation sections for system branch operations
 ----------------------------------------------------
 
diff --git a/yarns/morph.shell-lib b/yarns/morph.shell-lib
index 4fb1eb10..41ffbbbd 100644
--- a/yarns/morph.shell-lib
+++ b/yarns/morph.shell-lib
@@ -144,6 +144,27 @@ assert_morphologies_are_petrified()
 }
 
 
+nullify_local_refs()
+{
+    python -c 'import yaml, sys
+repo = sys.argv[1]
+ref = sys.argv[2]
+for filename in sys.argv[3:]:
+    with open(filename, "r") as f:
+        d = yaml.load(f)
+    if "strata" in d:
+        for spec in d["strata"]:
+            if spec["repo"] == repo and spec["ref"] == ref:
+                spec["repo"] = spec["ref"] = None
+    if "build-depends" in d:
+        for spec in d["build-depends"]:
+            if spec["repo"] == repo and spec["ref"] == ref:
+                spec["repo"] = spec["ref"] = None
+    with open(filename, "w") as f:
+        yaml.dump(d, f)
+' "$@"
+}
+
 # Currently, yarn isn't setting $SRCDIR to point at the project source
 # directory. We simulate this here.