RegEx for Markdown unordered lists

I need help selecting the `-` in unordered lists WITHOUT selecting dashes with a space anywhere else in the document. See my [regexr.com expression](https://regexr.com/76tfi) for my current RegEx. I also need blockquotes to accept any character possible. I also need to differentiate between unordered lists and the `-` in diff blocks.

Start with the linked regexr.com expression and inspect the repository's current regular-expression behavior. Define how unordered-list dashes, blockquotes, and diff blocks should be distinguished, then verify the expression against examples covering each case.

Written by the indexing model from the issue text.