I have made a new repo or a branch. Yes, but I typically keep it to myself and generate reports for others (if used at work).
EDIT: I was on mobile earlier, so extending my thoughts.
I typically make a new branch or repository but keep it on my own machine. I've gotten zero interest from colleagues in collaborating on this sort of thing, but they usually like the output. Org mode (my tool of choice, but not the only one) creates decent HTML output (you may want to play around with your own CSS or color schemes for the code blocks). So what I've done when we on-boarded a new project was to start doing this for certain critical sections that were under-documented. I then generated HTML output as a sort of white paper, and a PowerPoint deck that walked through the structure and control flow (would be best if I used flowcharts, but usually this is just text).
If we had good development machines at work, I'd definitely do the above with PlantUML or something similar to do text-based diagrams. Org will produce and embed images in the HTML output. This would make the flow for producing documentation much easier, I disliked trying to embed flowcharts created in Visio (tool available at work) into the HTML. I had to generate them, export to an image, link the image in org, and then keep it up to date manually. For a few charts it's not bad, but if you make a lot it's tedious to switch between tools and correctly export the image.
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For non-work stuff, I try to use literate programming from the start, but it's always solo projects so there's no "selling" this method. If I were collaborating with others, I'd have to reconsider the method. Leo has (from what I've read) an effective literate->code->literate story (that is, edit the code and the changes show back up in the literate format). Org mode can do that, but I haven't explored it. I'd really want that if I was to pursue literate programming in a collaborative environment (so that those uninterested in my method could still contribute).
[I had constructed a reply to your comment while it was being edited so when I posted the comment was much longer and had provided more than enough detail! Revised this comment accordingly]
EDIT: I was on mobile earlier, so extending my thoughts.
I typically make a new branch or repository but keep it on my own machine. I've gotten zero interest from colleagues in collaborating on this sort of thing, but they usually like the output. Org mode (my tool of choice, but not the only one) creates decent HTML output (you may want to play around with your own CSS or color schemes for the code blocks). So what I've done when we on-boarded a new project was to start doing this for certain critical sections that were under-documented. I then generated HTML output as a sort of white paper, and a PowerPoint deck that walked through the structure and control flow (would be best if I used flowcharts, but usually this is just text).
If we had good development machines at work, I'd definitely do the above with PlantUML or something similar to do text-based diagrams. Org will produce and embed images in the HTML output. This would make the flow for producing documentation much easier, I disliked trying to embed flowcharts created in Visio (tool available at work) into the HTML. I had to generate them, export to an image, link the image in org, and then keep it up to date manually. For a few charts it's not bad, but if you make a lot it's tedious to switch between tools and correctly export the image.
=====
For non-work stuff, I try to use literate programming from the start, but it's always solo projects so there's no "selling" this method. If I were collaborating with others, I'd have to reconsider the method. Leo has (from what I've read) an effective literate->code->literate story (that is, edit the code and the changes show back up in the literate format). Org mode can do that, but I haven't explored it. I'd really want that if I was to pursue literate programming in a collaborative environment (so that those uninterested in my method could still contribute).