When #207 is detected, leave the repo in a state that prevents furthe…

…r breakage

cinnabar/githg.py

@@ -601,6 +601,7 @@ def __init__(self):
         self._replace = Git._replace
         self._tagcache_ref = None
         self._metadata_sha1 = None
+        broken = None
         # While doing a for_each_ref, ensure refs/notes/cinnabar is in the
         # cache.
         for sha1, ref in Git.for_each_ref('refs/cinnabar',
@@ -613,6 +614,10 @@ def __init__(self):
                 self._metadata_sha1 = sha1
             elif ref == b'refs/cinnabar/tag_cache':
                 self._tagcache_ref = sha1
+            elif ref == b'refs/cinnabar/broken':
+                broken = sha1
+        self._broken = broken and self._metadata_sha1 and \
+            broken == self._metadata_sha1
         self._replace = VersionedDict(self._replace)
 
         self._tagcache = {}
@@ -1246,6 +1251,7 @@ def close(self, refresh=()):
             ) as commit:
                 for sha1, target in util.iteritems(self._replace):
                     commit.filemodify(sha1, target, b'commit')
+            self._metadata_sha1 = commit.sha1
 
         for c in self._tagcache:
             if c not in changeset_heads:
@@ -1326,6 +1332,7 @@ def tagset_lines(tags):
                 bundle = "Please keep a copy of the "
                 bundle += os.environ["GIT_DIR"] + "/cinnabar-last-bundle file"
                 bundle += " before doing the following.\n"
+            Git.update_ref(b'refs/cinnabar/broken', self._metadata_sha1)
             raise Abort(
                 "It seems you have hit a known, rare, and difficult to "
                 "reproduce issue.\n"

cinnabar/remote_helper.py

@@ -383,6 +383,10 @@ def list(self, arg=None):
         self._helper.flush()
 
     def import_(self, *refs):
+        if self._store._broken:
+            raise Abort('Cannot fetch with broken metadata. '
+                        'Please fix your clone first.\n')
+
         # If anything wrong happens at any time, we risk git picking
         # the existing refs/cinnabar refs, so remove them preventively.
         for sha1, ref in Git.for_each_ref('refs/cinnabar/refs/heads',
@@ -470,11 +474,16 @@ def push(self, *refspecs):
         pushes = list((Git.resolve_ref(fsdecode(s.lstrip(b'+'))), d,
                        s.startswith(b'+'))
                       for s, d in (r.split(b':', 1) for r in refspecs))
-        if not self._repo.capable(b'unbundle'):
+        if self._store._broken or not self._repo.capable(b'unbundle'):
             for source, dest, force in pushes:
-                self._helper.write(
-                    b'error %s Remote does not support the "unbundle" '
-                    b'capability\n' % dest)
+                if self._store._broken:
+                    self._helper.write(
+                        b'error %s Remote does not support the "unbundle" '
+                        b'capability\n' % dest)
+                else:
+                    self._helper.write(
+                        b'error %s Cannot push with broken metadata. '
+                        b'Please fix your clone first.\n' % dest)
             self._helper.write(b'\n')
             self._helper.flush()
         else: