List complete nodes which have a given child using sed.

list_dependency_graphs_sed.sh

# sometimes we have a hierarchical list and we want to print all of the nodes
# that have a certain child, simple regular expression will only yield the child
# not the whole node. We can use sed to recover the whole node.
#
# let's say we want to recover all packages in pipenv graph that use pandas.
# /^ /!x{...}
#   all of lines which do not start with a space are at the top of the
#   hierarchy, swap them with the hold space. The hold space has now the node
#   and the pattern space contains the contents of the hold space. Execute all
#   commands between brackets.
#
# /pandas/p
#   if we were at a node, we would have swapped the contents of the pattern
#   space with those of the hold space. In this case, we are lookin at the node
#   and all its children. Is `pandas` in there? Then print it.
#   if we are not at a node, we are lookin at a single line. This line will
#   never have a newline character. Thus, even if we had pandas in there we
#   would not print it.
#
# /^ /H
#   if we are looking at one of the children, then just append it to the hold
#   space.
pipenv graph | sed -n -e '/^ /!{;x; /pandas/p;}; /^ /H'

# similarly, we can find only the options we want, with the respective context with the below
pipenv run pytest --help | sed -E -n -e '/^ *--?/{;x; /(deselect|ignore)/p;}; /^ *--?/!H'