Permit existing users/groups

[Jonathan Perkin <jperkin%joyent.com@localhost>]

Hi,

Currently, if:

 * PKG_UID or PKG_GID are specified
 * the user/group already exists
 * the existing uid/gid do not match PKG_UID/PKG_GID

the failure mode is pretty rough, the package will be left in a
half-limbo state whilst pkg_add will continue to try installing
further packages which fail in weird and wonderful ways.

I'd like to fix this, and to also provide a user-defined option which
configures how pkg_install should proceed when provided a static
uid/gid which conflicts with the existing system.

My initial patch is available here:

  
https://github.com/joyent/pkgsrc/commit/e9d7ae57d011bdd9e1768848da6403ec72b2d599

It introduces a new user variable 'PKGINSTALL_IGNORE_UIDGID'.  This
defaults to 'no', where it will not permit a user/group uid/gid
mismatch (not yet implemented).  Set it to 'yes' and if the user/group
already exists then they will be re-used.

It is untested and incomplete, but I wanted to introduce this to the
list now whilst my bulk builds with it are running so that we can
discuss any issues or further requirements, as I'd really like to get
this in before the 2013Q2 freeze which is coming up fast.

Thanks,

-- 
Jonathan Perkin  -  Joyent, Inc.  -  www.joyent.com