Gnucap for Debian
-----------------
With the arrival of the shared library, the gnucap package has been split into
several packages.

The the new gnucap package replace the former package in terms of
functionality. The program /usr/bin/gnucap has become a tiny executable that
- no longer statically links the default plugins, but they are
  loaded by default (see below) and with
- most functionality transferred to libgnucap.
- Plugin choices can be overridden in /etc/gnucap.rc.

The library is libgnucap.so.0. it is expected not to change in relevant ways,
but if it does, will move to libgnucap.so.1. This will not break programs
linked against libgnucap.so.0, but it may affect the creation of new plugins
for these programs.

The package gnucap-default-plugins0 contains the default plugins. These are
installed to /usr/lib/<multiarch>/gnucap0/. The "0" indicates the relation to
libgnucap0.  This is the library, these plugins have been tested with. In the
past, plugins have been forward compatible. The library libgnucap provides a
command for loading plugins. It loads from the path specified in the
environment variable GNUCAP_PLUGPATH (colon separated, first wins, like PATH,
PYTHONPATH etc.).

The program /usr/bin/gnucap sets the GNUCAP_PLUGPATH environment to
/usr/lib/<multiarch>/gnucap0, if its empty or unset. This is where further
packages are expected to install plugins to. Other programs are expected to
query "gnucap-conf --pkglibdir" at configure time, hardwire that in a similar
way, and set the environment accordingly, when making use of the load command
in libgnucap. gnucap-conf is provided by the gnucap-common package.

The gnucap-common package contains some architecture independent files,
headers, and /usr/bin/gnucap-conf. This package determines the place where
additional plugins should be installed to, `gnucap-conf --pkglibdir`. This
makes sense, because plugins are compiled against the headers from this very
package.

The libgnucap-dev package ships the development library symlink, necessary to
build/link programs with the functionality of /usr/bin/gnucap.

 -- Felix Salfelder <felix@salfelder.org>, April 2018
