nix ls-nar: allow reading from FIFOs

fixes #2528

SSL certificate search failed to find user profile certificates.

This ensures that they can't write to /nix/store. Fixes #2535.

manual: quote $servlets

manual: fix typo (s/gift/git/)

This reverts commit 5a1a8708. Counting
is hard.

Fix manual build

This was broken by some missing closing tags in 0bea4a50

Deprecate builtins.toPath

Closes #179.

preferLocalBuild does not in fact prevent substitution.

Since we're not using multi-part uploads at the moment, we can drop
this patch.

Fix typo in comments

config: use all of XDG_CONFIG_DIRS

Previously, config would only be read from XDG_CONFIG_HOME. This change
allows reading config from additional directories, which enables e.g.
per-project binary caches or chroot stores with the help of direnv.

The use of TransferManager has several issues, including that it
doesn't allow setting a Content-Encoding without a patch, and it
doesn't handle exceptions in worker threads (causing termination on
memory allocation failure).

Fixes #2493.

Since the callback is global we can't refer to 'path' in it. This
could cause a segfault or printing of arbitrary data.

copyStorePath: Fix hash errors when copying from older store

This commit partially reverts 48662d15. When
copying from an older store (in my case a store running Nix 1.11.7), nix would
throw errors about there being no hash. This is fixed by recalculating the hash.

Bump fallback editline expression to latest in nixpkgs.

nix doctor: return nonzero exitcode if a check fails

This makes it easier to use this when testing the installer or when
running the checks with other automated tooling.

stdenv relies on this. So ignore self-references (but only in legacy non-structured attributes mode).