Administrative tool to download or delete files to/from the cache.

If /etc/apk/cache is a symlink to directory, a copy of all installed
packages is stored there, and the index of remote repositories will
be there instead of /var/lib/apk. This enables to reconstruct running
system during boot.

Left as todo: remove cached copy when the package is removed, and
additional apk applet to download missing packages to cache and/or
remove extra items.

And use it in couple of places. Some whitespace fixes too.

And add some more verbosity to the help message.

That will make the upgrade prefer packages available in repositories.
This is good if one want's to downgrade packages by removing an experimental
repository. Or to force re-install of locally built vs. repository version
when the package version are same, but checksum is different. Fixes #51.

Currently just goes through all world dependencies and updates them
where possible (ref #51).

We want be able to compare blobs so we basicly revert the old change,
and make a wrapper that takes version strings.

make apk_version_compare() take strings rather than blobs
add apk_pkgversion_compare(), a wrapper that takes packages

We might want to add an --update-index option to misc applets. For
example:

  apk add --update-index -u package
  apk version --update-index

and re-arrange the order of displayed info

By using a bitmask we can combine subactions

apk --help will list the generic options only and give a list of commands
To get the details for a spefic command, 'apk command --help' should be used.

Support version numbers specified with packages. For example:

 apk add 'busybox<1.14'
 apk add 'squid=>3.0'

since we dont verify the checksum we dont need to calculate it
Speed up when you try fetch lots of stuff thats already there.

We need to close the fd on destruction. This is what the corresponding
istream variant does too.

According the manpage readlink(2) does not append a null byte to buf.
So we have to do it ourselves.

Otherwise the iso image will have softlinks which is not what we want

leftovers from a debug session.

fixes #42

This will also fix a bug that left an empty file in destination dir when
source file did not exist in repository.

There are still issues with paths longer than 255 chars.

So we don't get local modifications or extra files in the tarball.

we should always close the in-stream, not only on failure.

This reverts commit 0906a1c7.

Conflicts:

	src/add.c

saves space

We upgrade when we have an oldpkg.

By locking all the given dependendencies for virtual packages first
we can catch invalid deps and report those. This is alot more helpful
than just reporting "Unable to install <virutalpkg>"

implements 'apk add --virutal metaname dep1 dep2...' where metaname will
be an empy meta package with dep1 and dep2 as dependencies.

This is useful to prevent abuild to add each makedepend to world which
causes some headache when it comes to unintalling them after sucessful build.

The syntax is: apk index -d /path/to/APK_INDEX.gz pkg...

It does not seem like its possible to remove packages in the db so we
trick apk_db_index_write() by setting the repo to on-zero.

It's still not perfect since it does not recalculate the dependencies.