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bzrlib/revision.py
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            except bzrlib.errors.NoSuchRevision, e:
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                pass
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        raise e
 
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def get_intervening_revisions(ancestor_id, rev_id, rev_source, 
 
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                              revision_history=None):
 
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    """Find the longest line of descent from maybe_ancestor to revision.
 
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    Revision history is followed where possible.
 
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    If ancestor_id == rev_id, list will be empty.
 
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    Otherwise, rev_id will be the last entry.  ancestor_id will never appear.
 
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    If ancestor_id is not an ancestor, NotAncestor will be thrown
 
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    """
 
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    [rev_source.get_revision(r) for r in (ancestor_id, rev_id)]
 
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    if ancestor_id == rev_id:
 
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        return []
 
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    def historical_lines(line):
 
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        """Return a tuple of historical/non_historical lines, for sorting.
 
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        The non_historical count is negative, since non_historical lines are
 
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        a bad thing.
 
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        """
 
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        good_count = 0
 
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        bad_count = 0
 
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        for revision in line:
 
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            if revision in revision_history:
 
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                good_count += 1
 
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            else:
 
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                bad_count -= 1
 
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        return good_count, bad_count
 
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    active = [[rev_id]]
 
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    successful_lines = []
 
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    while len(active) > 0:
 
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        new_active = []
 
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        for line in active:
 
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            parent_ids = [p.revision_id for p in 
 
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                          rev_source.get_revision(line[-1]).parents]
 
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            for parent in parent_ids:
 
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                line_copy = line[:]
 
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                if parent == ancestor_id:
 
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                    successful_lines.append(line_copy)
 
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                else:
 
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                    line_copy.append(parent)
 
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                    new_active.append(line_copy)
 
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        active = new_active
 
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    if len(successful_lines) == 0:
 
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        raise bzrlib.errors.NotAncestor(rev_id, ancestor_id)
 
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    for line in successful_lines:
 
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        line.reverse()
 
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    if revision_history is not None:
 
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        by_historical_lines = []
 
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        for line in successful_lines:
 
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            count = historical_lines(line)
 
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            by_historical_lines.append((count, line))
 
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        by_historical_lines.sort()
 
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        if by_historical_lines[-1][0][0] > 0:
 
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            return by_historical_lines[-1][1]
 
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    assert len(successful_lines)
 
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    successful_lines.sort(cmp, len)
 
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    return successful_lines[-1]