- A list of tuples indicating the edges between the current node and its

        parents.

    """

    branch_cache = {}

    def branch(rev):

        """Return branch for rev, using cache for efficiency.

        For Mercurial, always return the named branch name (which may be 'default').

        For Git, return a branch name for branch heads, otherwise None."""

        if rev not in branch_cache:

            branch_cache[rev] = repo[rev].branch

        return branch_cache[rev]

    row = []  # the ancestor revision that each column is tracking

    colors = {}  # color number for revisions - set by descendants

    obs = {}  # obsolete flag for revisions - set by descendants

    newcolor = 1  # the next available color

    for (rev, dagparents) in dag:

        # Compute row and nextrow

        if rev not in row:

            row.append(rev)  # new head

            colors[rev] = newcolor

            obs[rev] = int(repo[rev].obsolete)

            newcolor += 1

        col = row.index(rev)

        addparents = [p for p in dagparents if p not in row]

        # Add unknown parents to nextrow

        tmprow = row[:]

        tmprow[col:col + 1] = reversed(addparents) # highest revs first (to the right), dead ends last (to the left)

        # Filter old fake parents but keep new ones

        nextrow = []

        for r in tmprow:

            if r >= 0 or r in dagparents:

                nextrow.append(r)

            else:

                colors.pop(r)

                obs.pop(r)

        # Let color and obs for this rev be "inherited" by the first "parent"

        color = colors.pop(rev)

        if addparents:

            b = branch(rev)

            searching = True

            for p in reversed(addparents):

                if searching and branch(abs(p)) in [b, None]:

                    # This is the first parent on the same branch - inherit the color

                    colors[p] = color

                    searching = False # make sure we don't give the color away twice

                else:

                    colors[p] = newcolor

                    newcolor += 1

        # Add edges to the graph

        edges = []

        for ecol, ep in enumerate(row):

            if ep in nextrow:

                edges.append((ecol, nextrow.index(ep), colors[ep], obs[ep]))

            elif ep == rev:

                for p in dagparents:

                    edges.append((ecol, nextrow.index(p), colors[p], obs[p]))

        # Yield and move on

        closing = int(repo[rev].closesbranch)

        obsolete = int(repo[rev].obsolete)

        bumped = int(repo[rev].bumped)

        divergent = int(repo[rev].divergent)

        extinct = int(repo[rev].extinct)

        unstable = int(repo[rev].unstable)

        yield ((col, color), edges, closing, obsolete, bumped, divergent, extinct, unstable)

        row = nextrow