extend https://gist.github.com/junegunn/8b572b8d4b5eddd8b85e5f4d40f17236

ex-function.sh

# unique MRC(most recently checkouted, like MRU) checkouted branchs or commit hashs -> branch name or commit hash
_gm() {
    is_in_git_repo || return
    git --no-pager reflog | awk '$3 == "checkout:" && /moving from/ {print $8}' | uniq | \
        awk '
          BEGIN { memo[0]=""; results[0]=""; } { if(!($0 in memo))
          { memo[$0] = 1; results[length(results)] = $0; } }
          END { for(i=1; i<length(results); i++) print results[i] }
        ' | \
    fzf-down -m --preview 'git show --color=always {1}' --prompt="refs> "
}