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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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"""Topological sorting routines."""
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from __future__ import absolute_import
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revision as _mod_revision,
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from bzrlib import errors
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import bzrlib.revision as _mod_revision
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__all__ = ["topo_sort", "TopoSorter", "merge_sort", "MergeSorter"]
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graph -- sequence of pairs of node->parents_list.
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The result is a list of node names, such that all parents come before their
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The result is a list of node names, such that all parents come before
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node identifiers can be any hashable object, and are typically strings.
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This function has the same purpose as the TopoSorter class, but uses a
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different algorithm to sort the graph. That means that while both return a
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list with parents before their child nodes, the exact ordering can be
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topo_sort is faster when the whole list is needed, while when iterating
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over a part of the list, TopoSorter.iter_topo_order should be used.
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kg = _mod_graph.KnownGraph(dict(graph))
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return TopoSorter(graph).sorted()
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class TopoSorter(object):
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def __init__(self, graph):
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"""Topological sorting of a graph.
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:param graph: sequence of pairs of node_name->parent_names_list.
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i.e. [('C', ['B']), ('B', ['A']), ('A', [])]
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For this input the output from the sort or
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iter_topo_order routines will be:
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node identifiers can be any hashable object, and are typically strings.
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If you have a graph like [('a', ['b']), ('a', ['c'])] this will only use
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The graph is sorted lazily: until you iterate or sort the input is
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not processed other than to create an internal representation.
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iteration or sorting may raise GraphCycleError if a cycle is present
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iteration or sorting may raise GraphCycleError if a cycle is present
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# store a dict of the graph.
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# a dict of the graph.
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self._graph = dict(graph)
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self._visitable = set(self._graph)
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# self._original_graph = dict(graph)
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# this is a stack storing the depth first search into the graph.
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self._node_name_stack = []
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# at each level of 'recursion' we have to check each parent. This
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# stack stores the parents we have not yet checked for the node at the
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# matching depth in _node_name_stack
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self._pending_parents_stack = []
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# this is a set of the completed nodes for fast checking whether a
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# parent in a node we are processing on the stack has already been
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# emitted and thus can be skipped.
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self._completed_node_names = set()
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"""Sort the graph and return as a list.
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After calling this the sorter is empty and you must create a new one.
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return list(self.iter_topo_order())
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def iter_topo_order(self):
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"""Yield the nodes of the graph in a topological order.
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After finishing iteration the sorter is empty and you cannot continue
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visitable = set(graph)
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# this is a stack storing the depth first search into the graph.
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pending_node_stack = []
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# at each level of 'recursion' we have to check each parent. This
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# stack stores the parents we have not yet checked for the node at the
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# matching depth in pending_node_stack
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pending_parents_stack = []
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# this is a set of the completed nodes for fast checking whether a
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# parent in a node we are processing on the stack has already been
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# emitted and thus can be skipped.
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completed_node_names = set()
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# now pick a random node in the source graph, and transfer it to the
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# top of the depth first search stack of pending nodes.
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node_name, parents = graph.popitem()
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pending_node_stack.append(node_name)
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pending_parents_stack.append(list(parents))
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# loop until pending_node_stack is empty
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while pending_node_stack:
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parents_to_visit = pending_parents_stack[-1]
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# if there are no parents left, the revision is done
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# top of the depth first search stack.
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node_name, parents = self._graph.popitem()
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self._push_node(node_name, parents)
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while self._node_name_stack:
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# loop until this call completes.
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parents_to_visit = self._pending_parents_stack[-1]
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# if all parents are done, the revision is done
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if not parents_to_visit:
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# append the revision to the topo sorted list
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# all the nodes parents have been added to the output,
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# now we can add it to the output.
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popped_node = pending_node_stack.pop()
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pending_parents_stack.pop()
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completed_node_names.add(popped_node)
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# all the nodes parents have been added to the output, now
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# we can add it to the output.
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yield self._pop_node()
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# recurse depth first into a single parent
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next_node_name = parents_to_visit.pop()
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if next_node_name in completed_node_names:
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# parent was already completed by a child, skip it.
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if next_node_name not in visitable:
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# parent is not a node in the original graph, skip it.
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# transfer it along with its parents from the source graph
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# into the top of the current depth first search stack.
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parents = graph.pop(next_node_name)
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# if the next node is not in the source graph it has
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# already been popped from it and placed into the
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# current search stack (but not completed or we would
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# have hit the continue 6 lines up). this indicates a
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raise errors.GraphCycleError(pending_node_stack)
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pending_node_stack.append(next_node_name)
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pending_parents_stack.append(list(parents))
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while self._pending_parents_stack[-1]:
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# recurse depth first into a single parent
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next_node_name = self._pending_parents_stack[-1].pop()
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if next_node_name in self._completed_node_names:
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# this parent was completed by a child on the
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# call stack. skip it.
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if next_node_name not in self._visitable:
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# otherwise transfer it from the source graph into the
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# top of the current depth first search stack.
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parents = self._graph.pop(next_node_name)
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# if the next node is not in the source graph it has
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# already been popped from it and placed into the
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# current search stack (but not completed or we would
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# have hit the continue 4 lines up.
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# this indicates a cycle.
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raise errors.GraphCycleError(self._node_name_stack)
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self._push_node(next_node_name, parents)
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# and do not continue processing parents until this 'call'
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def _push_node(self, node_name, parents):
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"""Add node_name to the pending node stack.
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Names in this stack will get emitted into the output as they are popped
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self._node_name_stack.append(node_name)
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self._pending_parents_stack.append(list(parents))
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"""Pop the top node off the stack
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The node is appended to the sorted output.
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# we are returning from the flattened call frame:
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# pop off the local variables
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node_name = self._node_name_stack.pop()
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self._pending_parents_stack.pop()
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self._completed_node_names.add(node_name)
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def merge_sort(graph, branch_tip, mainline_revisions=None, generate_revno=False):
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"""Topological sort a graph which groups merges.
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:param graph: sequence of pairs of node->parents_list.
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:param branch_tip: the tip of the branch to graph. Revisions not
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:param branch_tip: the tip of the branch to graph. Revisions not
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reachable from branch_tip are not included in the
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:param mainline_revisions: If not None this forces a mainline to be
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C is the end of a cluster due to rule 1.
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D is not the end of a cluster from rule 1, but is from rule 2: E
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D is not the end of a cluster from rule 1, but is from rule 2: E
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is not its left most ancestor
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E is the end of a cluster due to rule 1
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F might be but we need more data.
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we show connecting lines to a parent when:
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- The parent is the start of a merge within this cluster.
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That is, the merge was not done to the mainline before this cluster
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That is, the merge was not done to the mainline before this cluster
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was merged to the mainline.
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This can be detected thus:
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* The parent has a higher merge depth and is the next revision in
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* The parent has a higher merge depth and is the next revision in
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The next revision in the list constraint is needed for this case:
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B 1 [C, F] # we do not want to show a line to F which is depth 2
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B 1 [C, F] # we do not want to show a line to F which is depth 2
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C 1 [H] # note that this is a long line to show back to the
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C 1 [H] # note that this is a long line to show back to the
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ancestor - see the end of merge rules.
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# the scheduling order is: F, E, D, C, B, A
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# the scheduling order is: F, E, D, C, B, A
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# that is - 'left subtree, right subtree, node'
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# which would mean that when we schedule A we can emit the entire tree.
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self._scheduled_nodes = []
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# This records for each node when we have processed its left most
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# This records for each node when we have processed its left most
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# unmerged subtree. After this subtree is scheduled, all other subtrees
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# have their merge depth increased by one from this nodes merge depth.
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# it contains tuples - name, merge_depth
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if not left_subtree_pushed_stack[-1]:
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# recurse depth first into the primary parent
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next_node_name = pending_parents_stack[-1].pop(0)
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is_left_subtree = True
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left_subtree_pushed_stack[-1] = True
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# place any merges in right-to-left order for scheduling
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# which gives us left-to-right order after we reverse
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# the scheduled queue. XXX: This has the effect of
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# the scheduled queue. XXX: This has the effect of
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# allocating common-new revisions to the right-most
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# subtree rather than the left most, which will
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# subtree rather than the left most, which will
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# display nicely (you get smaller trees at the top
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# of the combined merge).
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next_node_name = pending_parents_stack[-1].pop()
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is_left_subtree = False
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if next_node_name in completed_node_names:
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# this parent was completed by a child on the
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# call stack. skip it.
added
removed
bzrlib/tsort.py
