Improve handling of large diffs

This MR adjusts the way checking for large diffs takes place. Prior to this MR the procedure was basically as follows:

1. Iterate over every diff in a collection
2. Just load the entire diff into memory, why not
3. Check if the resulting content including any diff markers/meta data exceed a threshold
4. Prune or collapse the diff

This MR changes things around so the procedure is instead as follows:

1. Iterate over every diff in a collection
2. Check if the data modified (excluding diff markers) is larger than a threshold
3. If this is not the case, proceed as usual. if this is the case we'll prune/collapse the diff