* doc: add stdenv passthru chapter
Broad strokes:
- create the chapter
- move existing stdenv passthru coverage into it
- move out-of-place coverage of passthru.tests from the stdenv meta chapter into it
- (try to) apply 1-sentence-per-line to text I've touched
- add legacy anchors for everything moved
- update existing links to the new anchors
- add tentative motivating text
- make nixpkgs-internal links relative/branchless
razor: if it is only ever needed by contributors, which is likely if links
refer to the latest revision of the source code, then it's for
the contributor guide
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
* doc: improve fetchers overview, deduplicate readme content
* Improve caveat explanation and some fetchurl content
* move out consumer docs on source fetching
* move note on mirror URLs to the relevant section
this may be better suited for the `fetchurl` reference, but it's probably better to
just render that information into the manual. for now, because
- contributor documentation encourages mirrors
- we can expect contributors to dig into the source
- linking source files is trivial in in-code documentation
we leave it there.
* move instructions for updating hashes to the manual
* Add more clarity on text, reorganise source hash methods
---------
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
Co-authored-by: Dominic Mills-Howell <dominic.millz27@gmail.com>
Co-authored-by: lolbinarycat <dogedoge61+github@gmail.com>
