add --unlink arg to 'butler prune-collection'

python/lsst/daf/butler/_butler.py

@@ -1204,7 +1204,8 @@ def removeRuns(self, names: Iterable[str], unstore: bool = True) -> None:
             # Point of no return for removing artifacts
             self.datastore.emptyTrash()
 
-    def pruneCollection(self, name: str, purge: bool = False, unstore: bool = False) -> None:
+    def pruneCollection(self, name: str, purge: bool = False, unstore: bool = False,
+                        unlink: Optional[List[str]] = None) -> None:
         """Remove a collection and possibly prune datasets within it.
 
         Parameters
@@ -1224,6 +1225,9 @@ def pruneCollection(self, name: str, purge: bool = False, unstore: bool = False)
         unstore: `bool`, optional
             If `True`, remove all datasets in the collection from all
             datastores in which they appear.
+        unlink: `list` [`str`], optional
+            Before removing the given `collection` unlink it from from these
+            parent collections.
 
         Raises
         ------
@@ -1246,7 +1250,20 @@ def pruneCollection(self, name: str, purge: bool = False, unstore: bool = False)
         if collectionType is not CollectionType.RUN and purge:
             raise PurgeUnsupportedPruneCollectionsError(collectionType)
 
+        def remove(child: str, parent: str) -> None:
+            """Remove a child collection from a parent collection."""
+            # Remove child from parent.
+            chain = list(self.registry.getCollectionChain(parent))
+            try:
+                chain.remove(name)
+            except ValueError as e:
+                raise RuntimeError(f"{name} is not a child of {parent}") from e
+            self.registry.setCollectionChain(parent, chain)
+
         with self.registry.transaction():
+            if (unlink):
+                for parent in unlink:
+                    remove(name, parent)
             if unstore:
                 for ref in self.registry.queryDatasets(..., collections=name, findFirst=True):
                     if self.datastore.exists(ref):

python/lsst/daf/butler/cli/cmd/commands.py

@@ -158,6 +158,10 @@ def config_validate(*args, **kwargs):
 @click.option("--unstore",
               help=("""Remove all datasets in the collection from all datastores in which they appear."""),
               is_flag=True)
+@click.option("--unlink",
+              help="Before removing the given `collection` unlink it from from this parent collection.",
+              multiple=True,
+              callback=split_commas)
 @options_file_option()
 def prune_collection(**kwargs):
     """Remove a collection and possibly prune datasets within it."""

python/lsst/daf/butler/script/pruneCollection.py

@@ -27,7 +27,7 @@
 )
 
 
-def pruneCollection(repo, collection, purge, unstore):
+def pruneCollection(repo, collection, purge, unstore, unlink):
     """Remove a collection and possibly prune datasets within it.
 
     Parameters
@@ -40,10 +40,12 @@ def pruneCollection(repo, collection, purge, unstore):
         Same as the ``purge`` argument to ``Butler.pruneCollection``.
     unstore: `bool`, optional
         Same as the ``unstore`` argument to ``Butler.pruneCollection``.
+    unlink: `list` [`str`]
+        Same as the ``unlink`` argument to ``Butler.pruneCollection``.
     """
     butler = Butler(repo, writeable=True)
     try:
-        butler.pruneCollection(collection, purge, unstore)
+        butler.pruneCollection(collection, purge, unstore, unlink)
     except PurgeWithoutUnstorePruneCollectionsError as e:
         raise TypeError("Cannot pass --purge without --unstore.") from e
     except RunWithoutPurgePruneCollectionsError as e: