Compare Rebase Script Fragment

compare_rebase.sh

compareRebase () {
	local newbranch oldbranch newcommit oldcommit ancestor
	local opts=()
	if [ "$1" = "-w" ]
	then
		opts+=("-w")
		shift
	fi
	newbranch=${1:-$(git rev-parse --abbrev-ref HEAD)}
	oldbranch=${2:-"${newbranch}@{u}"}
	ancestor=${3:-origin/master}
	oldancestor=${4:-"$ancestor"}
	oldcommit=$(git commit-tree -p "$(git merge-base "${oldancestor}" "${oldbranch}")" "${oldbranch}^{tree}" -m "before rebase")
	newcommit=$(git commit-tree -p "$(git merge-base "${ancestor}" "${newbranch}")" "${newbranch}^{tree}" -m "after rebase")
	git range-diff "${opts[@]}" "${oldcommit}^..${oldcommit}" "${newcommit}^..${newcommit}"
}

For comparison, I use this

#!/usr/bin/env bash

master=$1
: "${master:=master}"

colordiff -u \
          <(git diff "$(git merge-base "origin/$master" "HEAD@{u}")" "HEAD@{u}") \
          <(git diff "$(git merge-base "origin/$master" HEAD)" HEAD)

Utility for comparing the outcome of a rebase by comparing their diffs from a common ancestor (e.g. the master branch). Assumes that the branch's upstream is the "before" state to compare with.

The advantage of using git range-diff is that it gives you a proper colorized "diff-of-diffs", which can be very hard to read otherwise.