support updating of per app info by hooks

upgrade providers, new version gives error message for bad provider dep

hooks/artifacts are always run/resolved from an app unless at top of umbrella

Fix cover_spec options for ct

delete and prepend code path instead of replacing, fixes #770

add current_app attribute for setting before calling hooks

Fix #744: Allow _checkouts dep to override pkg dep not in registry

move state into app_info

Revert "Revert "only load packages when needed""

Revert "only load packages when needed"

only load packages when needed

Displays package caching actions

use ~ts for unicode output and reset encoding to latin1

Utf8 tree

This makes it obvious where packages are cached and when the cache is
being reused.

Messages are of the form:

===> Fetching recon ({pkg,<<"recon">>,<<"2.2.0">>})
===> Downloaded package, caching as
$HOME/.cache/rebar3/hex/default/packages/recon-2.2.0.tar

and

===> Fetching recon ({pkg,<<"recon">>,<<"2.2.0">>})
===> Version cached at
$HOME/.cache/rebar3/hex/default/packages/recon-2.2.0.tar is up
to date, reusing it

set parent on already fetched apps so tree works

Use raw bytestream when writing files

This patch forces write_file_if_contents_differ/2 to use raw bytes as
when writing files. This fixes an issue where UTF-8 characters are
processed and written back as ISO-8859-1 into the file, which makes it
impossible to use UTF-8 characters in .app.src files.

remove replacement of home dir with ~ in update output

symlink ct test dirs rather than copy