[jrbancel]

The most enlightening introduction to git internal model (graph of commits) and how the main commands alter it I have read so far: https://jwiegley.github.io/git-from-the-bottom-up/

I think it is slightly more relevant to understand the model than the .git/ structure since the .git/ folder is just an implementation detail.

[paulddraper]

The point of this is to also understand just the implementation.

[chmaynard]

Could someone please post a link to a PDF version of this article?

[blacksmith_tb]

For offline use? But git is a dvcs... ahem, anyhow, wkhtmltopdf[1] is a reasonable choice for converting arbitary urls to pdfs, and can be installed via apt, homebrew cask etc.

[1] http://wkhtmltopdf.org/