There appears to be multiple methods to customize the locations where (La)TeX search for files, as well as packages like import etc.
- What are they/how to use them?
- Why were they introduced? Why are there so many options?
- What's the difference between them?
- What commands do they affect? (e.g.
\input \include \@@input \openin \includegraphics \includepdf \lstinputlisting \VerbatimInputetc.)
