v1.10.0 changes the behavior of the command line client so that it can also fetch retweets from a file of tweet_ids.
twarc retweets ids.txt > retweets.jsonl
This is in addition to the previous behavior where it accepted a tweet id to fetch the retweets for:
twarc retweets 20 > retweets.jsonl
You can also comma separate the tweet ids on the command line if you want:
twarc retweets 20,21 > retweets.jsonl
The internal interface to the Twarc.reteets has changed to now accept an iterator of tweet ids.
python
from twarc import Twarc
twitter = Twarc()
for tweet in twitter.retweets([20, 21]):
print(tweet['id_str'])
etc
If you have been using the retweets method in your code you will want to adjust it to pass in a list of ids rather than the bare ids.