Co-authored-by: Jörg Thalheim <Mic92@users.noreply.github.com>

Since we've changed a lot of things in the 'nix' command (e.g. rename
'nix run') there is not much point in keeping this around.

nix/search: no error for empty search results if json is enabled

- result list will be always empty if --json is passed
- for scripts an empty search result is not really an error,
  we rather want to distinguish between evaluation errors and empty results

builtins.readFile: do not truncate content

Improve help-message for nix-repl

Use fragment size for autoGC capacity calculation

This reverts commit 3ebfbecd, reversing
changes made to c089c52d.

https://github.com/NixOS/nix/pull/3558

remote-store: don't log raw stderr by default

The raw stderr output isn't logged anymore so the build logs need to be
printed by the default logger in order for the old commands like
nix-build to still show build output.

For remote stores the log messages are already forwarded as structured
STDERR_RESULT messages so the old format is duplicate information.  But
still included with -vvv since it could be useful for debugging
problems.

    $ nix build -L /nix/store/nl71b2niws857ffiaggyrkjwgx9jjzc0-foo.drv --store ssh-ng://localhost
    Hello World!
    foo> Hello World!
    [1/0/1 built] building foo

Fixes #3556

* Remove obsolete `printHelp` function
* Add an example to demonstrate how to list all available commands
  within the REPL

(cherry picked from commit f459ca54)

(cherry picked from commit 5d8504b9)

(cherry picked from commit bc5d4843)

Revamp README.md

Co-authored-by: worldofpeace <worldofpeace@protonmail.ch>

Co-authored-by: worldofpeace <worldofpeace@protonmail.ch>

Rename nix app and nix run commands

This avoids inheriting the caller's shellHook, which can happen when
running a dev-shell inside a dev-shell.

Tested against https://github.com/NixOS/nixpkgs/pull/72074.

Fixes #3540.