This document describes how libpkgconf was packaged for build2. In particular,
this understanding will be useful when upgrading to a new upstream version.
See ../README-DEV for general notes on pkgconf packaging.

Symlink the required upstream files and directories and provide our own
implementations for auto-generated headers:

$ ln -s ../upstream/{AUTHORS,COPYING} ./

$ ln -s ../../upstream/libpkgconf/config.h.cmake.in \
  libpkgconf/config.h.cmake.in.orig

$ cd libpkgconf && ln -s ../../upstream/libpkgconf/*.{c,h} ./

Use libpkgconf/config.h.cmake.in.orig for creating libpkgconf/config.h and
libpkgconf/version.h.in, defining/undefining macros introduced with
#cmakedefine.

Re-creating libpkgconf/config.h from scratch every time we upgrade to a new
upstream version would be a real pain. Instead we can only (un)define the
newly introduced macros, comparing the already defined and currently used
macro sets:

$ for m in `cat libpkgconf/config.h.cmake.in.orig | \
            sed -n 's/.*#\s*cmakedefine\s\{1,\}\([_a-zA-Z0-9]\{1,\}\)\(\s.*\)\{0,1\}$/\1/p' | sort -u`; do
    if grep -q -e "\b$m\b" `find -L . -name '*.h' -a ! -name config.h -a ! -name version.h -o -name '*.c'`; then
      echo "$m"
    fi
  done >used-macros

$ cat libpkgconf/config.h |
  sed -n 's/#\s*\(define\|undef\)\s\{1,\}\([_a-zA-Z0-9]\{1,\}\)\(\s.*\)\{0,1\}$/\2/p' |
  sort -u >defined-macros

$ diff defined-macros used-macros >diff-macros