Xml in packaging system

[Galen Sampson]

Matthew Dillon wrote:
    What I envision in a packaging system is something that makes the 
    port maintainer's life as easy as possible.

    Lets say you are developing a new port, libabcd, which depends on a
    number of other libraries which are also ports in the system.
    As a developer I want to be able to do something like this:

    % vfsenvironment empty 'csh'

    (Now you would be in a vfs-sandboxed shell.  You can map-in other ports
    which you have already installed on the system):
    % vfsrecord "build_depend"
    ok, recording mappings as 'build_depend'
    % vfsmap libgettextsrc:0.12.11
    ok
    % vfsmap libexpat		(map in the highest installed version)
    ok
    % vfsmap libc
    ok
    % vfsmap gmake
    % vfsrename /usr/local/bin/gmake /usr/local/bin/make
    Once you have built an environment you could then attempt to build
    your new port natively simply by running the port's native build
    (at least initially).  If things are missing you can vfsunmap and vfsmap
    additional required elements.
    Modifications to the port distribution itself could also be done through
    the VFS.  In this case the VFS would be acting like a unionfs in that it
    would record whiteouts (deletions) and copy files that are modified into
    a higher layer which would be stored in the VFS environment process's
    memory (sufficient as long as no more then 2G worth of changes are made).
    % vfsunion ~dillon/original_distribution work

    (make your modifications to the work.  edit files, rm files, rename, 
    whatever).

    When you are satisfied that the build is working you can save the vfs
    state, which will also 'diff' any modifications you have made and record
    file/directory deletions.  The output file would be human readable and
    human editable (though it's easier for the developer to just enter the
    vfs environment and make modifications within the environment)
    % vfsrecord -w
    all changes recorded in 'build_depend.vfs'
    % exit
    --------------------

    Ok.  So there you have it, you now have the VFS environment and the
    patches required to build your new port!
    Similar action would be taken for install and run-time dependancies.
    Run-time dependancies would be more restrictive since under normal
    conditions you might not want to have to run every port wrapped in a 
    VFS.  e.g. simple ports like when you run 'less'.  But more involved
    ports, like OpenOffice, might always run in some sort of VFS environment.

    Note that the VFS environment I am contemplating does not take over
    the entire filesystem space.  That is, in the above example, the mainstream
    directories /usr/local/lib and /usr/local/bin would be selectively enabled
    and/or modified within the VFS but other directories, like your home
    directory for example (really all other directories not involved with
    mapping operations) would simply be passed through.  You would have to
    explicitly tell the VFS to map something as a union in order for the VFS
    to record your modifications within that target.
    In anycase, that is my idea... to approach it from the port maintainer's
    point of view rather then from a technical standpoint.
This is excellent.  What you have described here describes the build 
configuration.  You mention that the install dependencies would be 
similar.  My question is about package lists.  When I install this port 
that I have set up would the package list stay static like the 
pkg-plist, or would it be possible to be dynamic (i.e. record what is 
installed and save that is the package list).  Say I'm about to `make 
install` or equivalent for this port I'm creating (libabcd in your 
example).  I assume it would be something like:

% vfsenvironment install_depend.vfs 'csh'
(Read in the environment that is required for installation of libabcd)
% vfsrecord "install"
% vfssnapshot ${PREFIX} install.vfssnap
Record current state of ${PREFIX} and save it in install.vfssnap for 
`diffing` after install.

% make install
% vfsunion install.vfssnap ${PREFIX}
% vfsrecord -w
all changes to ${PREFIX} recorded in 'install.vfs'
% exit
The reason a snapshot would need to be recorded is I can't vfsunion to 
something that doesn't exist yet.  Maybe instead of creating a snapshot 
there could be a `vfsmonitor ${PREFIX}` which would record changes to a 
filesystem instead of creating a (potentially huge) snapshot.  The idea 
is that packages with the same version do not always install the same 
files depending on which knobs are turned during configure, or 
equivalent.  I want the information about the package installed on my 
system to accurately reflect what was installed, not what the person who 
generated a plist had insalled for them.  I just had this happen with 
freebsd during installation of kerberos5.  I didn't install kerberos4 
compatibility, and hence the package would not be created because of 
missing files.  I had to edit the plist because I turned some knobs in a 
makefile.

regards,
Galen