列出切換 branch 前需要 rollback 的 South migration。

ls-migrations-then-checkout

#!/usr/bin/env zsh

if [[ $# != 1 ]]; then
    cat - << USAGE
Usage: `basename $0` <branch>
USAGE
    return 1
fi

local old_branch=$(git rev-parse --abbrev-ref HEAD)
local new_branch=$(git rev-parse --abbrev-ref $1)

if [[ $new_branch == $old_branch ]]; then
    echo "# No changes"
    return
fi

local merge_base=$(git merge-base $old_branch $new_branch)

awk -f <( cat - <<'SCRIPT'
    migrations[$1] <= 0 || $2 < migrations[$1] {
        migrations[$1]=$2
    }

    END {
        if (length(migrations) > 0) {
            print "# Migrations neeed to rollback:"
            for (app in migrations) {
                last = migrations[app] - 1;
                if (last>0) {
                    printf "./manage.py migrate %s %04d\n", app, last
                } else {
                    printf "./manage.py migrate %s zero\n", app
                }
            }
            print ""
        }
    }
SCRIPT
) <(
    git diff --name-only --diff-filter=A \
            --relative=$(git rev-parse --show-prefix) \
            $merge_base $old_branch \
        | grep -E '/migrations/[0-9]{4}.+py' \
        | sed -E -e 's,/migrations/, ,' -e 's/( [0-9]{4}).+$/\1/'
)
echo "# Checkout new branch:"
echo "git checkout $new_branch"
echo
echo "# Migrate"
echo "./manage.py migrate"

如果有 app 在 new branch 才有 migration 的話會失效。