SQLite is open-source but not open-contribution – they don't accept contributions of that sort. They follow "cathedral" style development and invented a whole alternative to git for that purpose https://fossil-scm.org/home/doc/43c3d95a/www/fossil-v-git.wi...
> In order to keep SQLite completely free and unencumbered by copyright, the project does not accept patches. If you would like to suggest a change and you include a patch as a proof-of-concept, that would be great. However, please do not be offended if we rewrite your patch from scratch.
https://www.sqlite.org/copyright.html
> In order to keep SQLite completely free and unencumbered by copyright, the project does not accept patches. If you would like to suggest a change and you include a patch as a proof-of-concept, that would be great. However, please do not be offended if we rewrite your patch from scratch.