cycle-branch.sh

#!/usr/bin/env bash

set -euo pipefail


git_dir="$(git rev-parse --git-dir)"

list_reflog_entries() {
	git log --walk-reflogs --grep-reflog '^checkout: moving from ' --format='%gs'
}


reflog_regex="^checkout: moving from [^[:space:]]+ to ([^[:space:]]+)$"

list_branches_with_duplicates() {
	while IFS= read -r line ; do 
		[[ "$line" =~ $reflog_regex ]] || continue
		target_branch="${BASH_REMATCH[1]}"
		echo "$target_branch"
	done < <(list_reflog_entries)
}

list_branches_unique() {
	list_branches_with_duplicates \
		| awk '{print NR " " $0}' \
		| sort -u -k 2 \
		| sort -n -k 1 \
		| cut -d' ' -f 2-
}

filter_valid_branches() {
	while IFS= read -r branch ; do
		if git show-ref --verify --quiet "refs/heads/${branch}" 2>/dev/null ; then
			echo "$branch"
		fi
	done
}

if [[ -x "$(which fzf 2>/dev/null)" ]]; then
	selected_branch="$(list_branches_unique | filter_valid_branches | fzf || true)"
	if [[ -n "${selected_branch}" ]]; then
		git checkout "$selected_branch"
	fi
else
	list_branches_unique | tail -r
fi