Couple of git and bash commands to generate list of commits (patches) and sort them by size to begin effort estimation.

estimate-porting-effort-using-commits.sh

# Generate alist of patches from a "base" commit-hash in the past to the HEAD.
# Run this on the source repository 
git format-patch --root <commit-hash> <optional-sub-dir> -o patches-from-commit-hash-to-HEAD/

# Generate a sorted (by LoC) list of patch files generate above to focus n the largests changes first.
# NOTE: Sometime, several "small" changes may introduce "dependencies" required by a large change down the line.
# Use "git blame -wCCC", "git log -S <string>" and "git gui blame" for code archaeology.
find ./patches-from-commit-hash-to-HEAD/ -type f -exec wc -l {} + | sort -rn | wc -l > 0000-list-of-commits-sorted-by-lines.txt