Use cache

[bact]

1. When user ask to update the database without specifying the licenst list version number, it means update to the latest version. Check the license list version in the database. If it is already the latest. Do not update.

2. When user ask to update the database with a specific license list version number. Check the license list version in the database. If it is already that specific version. Do not update.

3. Cache licenses.json (from https://spdx.org/licenses/licenses.json). Cache SPDX license data tarball. Cache GitHub license popularity data. Keep the files in the same directory as the SQLite database file.

   3.1) https://spdx.org/licenses/licenses.json contains latest license list version and release date
   3.2) https://spdx.org/licenses/licenses.json cache will expire after 45 days
   3.3) GitHub license popularity data cache will expire after 75 days
   3.4) SPDX license data is versioned, so it will not expired

4. When user put --force option (licenseid update --force), update the database without checking the license list version in the database. If cache license data of that version is available, use cache.

5. When user put --no-cache option (licenseid update --no-cache), don't use cache. Don't delete cache.

6. When user put --clear-cache option (licenseid update --clear-cache), delete cache.

7. When update the database, tell the user that the data source is from local file, from remote, or from cache of remote