rust-index: avoid some cloning in find_gca_candidates() Instead of keeping the information whether the current revision is poisoned on `current_seen`, we extract it as a boolean. This also allows us to simplify the explanation of `seen[r].is_poisoned()`, as the exceptional case where it is poisoned right after `r` has been determined to be a solution does no longer exist.

# Declare requirements for generating the compiled (frozen)
# set of requirements in ./requirements.txt.

docutils
jinja2