lookup proper directory instance as the tar output might not be
linear.

get list of overlay files from stdin, so those do not get overwritten.

less syscalls.

do not overwrite target if we have --never-overwrite and target exists.

ref #197

the old code treated a symlink to directory as file; it tried
to calculate regular has of it. fix this by: 1) using no follow
on migration and pruning stats, and 2) the helper function to
check if it's point to directory and not calculate hash in that
case. fixes #188.

ability embed description information to repository indexes
(e.g. repository name and version) and show it via "apk version -I".

check device major if it's tmpfs and refuse to use cache if
we've been fooled.

the first item is place holder for argv[0] = script name. it's
overwritten by the apk_pkgi_run_script.

- make virtual packages work again
- make apk del (for non-empty packages) work again

this makes the database package entry smaller, and we propbably
get more fields to installed_package later too. this cleans up
the way scripts are stored and is a preparation for supporting
triggers. some parsing for trigger meta-data. ref #45.

also have the output stream support writing to temporary file
and do renameat/unlinkat on close depending on if all writes
succeeded or not.

and take checksums for symlinks too.

otherwise, non repository files present in cache are not
considered for installation (e.g. when booting from cdrom).

fixes #127

some hooks to package verification code were missing causing the
verification to not be done (causing pre-script to be not run).
fixes #124, #126.

instead enforce world dependencies when the package name
is first referenced upon.

this helps boots sequence when network is not available.

so user can override trusted keys directory and repositories file.

it's a warning not an error to have non-existant repository.
bad signature means tampering; but we might want to just ignore
those. this is especially important if we have http repositories
and we are bootstrapping (without network).

over the ones in config file. also remove the apk_root == NULL
check as this cannot happen anymore. a valid root is always
required.

it will allow to overwrite files owned by some other packages
to get upgrades right (e.g. when splitting or renaming packages)

also makes it possibly to upgrade package without adding it to
top-level deps. fixes #69.

otherwise we can accept unsigned repositories, and install bad
packages.

should really fix abuild-tar.

other wise cache_fd points to var/lib/apk and contains the real
installed db causing it to be loaded twice.

this way we never change cwd, and relative filenames are always
parsed consistently. this also helps filename construction in many
places. this patch also changes '--root' to override location of
all configuration to be in the new root. previously it depended
on the file which one was used.

also take precautions in audit code if the db is missing the
checksum.

and use it for /etc/init.d by default. fixes #99.

we don't want to do checksumming of existing files unless it's
in a protected directory. also, we keep the original file if it's
*modified*.

and force checksumming only when unpacking archive. otherwise
it's extra computation for nothing.

use the package 'installed_size' == 0 as a test instead for
dependency only packages.

this enables virtual packages and files specified from command
line to work on non-harddisk installs.