How to enforce that the directory name must match the chart name?

In 2016, this used to be the default behavior in Helm:

fix(helm): produce error if package name is inconsistent

In 2018, this enforcement was removed:

remove dirname constraint on helm package

We would like to reintroduce this requirement in our Helm charts codebase, as a best practice, to prevent chart name collisions.

What would be the most native way to accomplish that?

I would probably write a git pre-commit hook if there is no native way (e.g. via some helm lint flag).

Use the following script with pre-commit:

#!/usr/bin/env bash
#
# Check that the directory name matches the chart name in Chart.yaml.
#
# Examples:
#   - foo/Chart.yaml with "name: hey-foo" fails the check.
#   - foo/Chart.yaml with "name: foo" passes the check.
#
# Usage: $0 [path/to/chart/Chart.yaml ...]

for chart in "$@"; do
    dirname="$(basename "$(dirname "$chart")")"

    # Remove trailing slash.
    dirname="${dirname%/}"

    # Fetch chart name from Chart.yaml.
    chart_name="$(yq e '.name' "$chart")"

    if [[ $dirname != "$chart_name" ]]; then
        echo "error: directory name '${dirname}' does not match chart name '${chart_name}'"
        exit 1
    fi
done