sci-mathematics/gap: PDEPEND on autoloaded packages without USE=minimal

This completes the rest of the dependency circle for GAP and the
packages that it sort-of depends on.

Signed-off-by: Michael Orlitzky <mjo@gentoo.org>

sci-mathematics/gap/gap-4.12.2-r2.ebuild

@@ -12,7 +12,7 @@ SRC_URI="https://github.com/gap-system/gap/releases/download/v${PV}/${P}-core.ta
 LICENSE="GPL-2+"
 SLOT="0/8"
 KEYWORDS="~amd64"
-IUSE="cpu_flags_x86_popcnt debug emacs memcheck readline test valgrind"
+IUSE="cpu_flags_x86_popcnt debug emacs memcheck minimal readline test valgrind"
 REQUIRED_USE="?? ( memcheck valgrind )"
 RESTRICT="!test? ( test )"
 
@@ -25,6 +25,29 @@ REQUIRED_PKGS="
 	dev-gap/smallgrp
 	dev-gap/transgrp"
 
+# The packages aren't really required, but GAP tries to load them
+# automatically, and will complain to the user if they fail to load.
+# The list of automatically-loaded packages is a user preference, called
+# AutoloadPackages, and the upstream default can be found in
+# lib/package.gi within the GAP source tree. Passing "-A" to GAP on the
+# CLI (or setting that user preference) will suppress the autoload
+# behavior and allow GAP to start without these, which is why we allow
+# the user to skip them with USE=minimal if he knows what he is doing.
+AUTOLOADED_PKGS="
+	dev-gap/autpgrp
+	dev-gap/alnuth
+	dev-gap/crisp
+	dev-gap/ctbllib
+	dev-gap/factint
+	dev-gap/fga
+	dev-gap/irredsol
+	dev-gap/laguna
+	dev-gap/polenta
+	dev-gap/polycyclic
+	dev-gap/resclasses
+	dev-gap/sophus
+	dev-gap/tomlib"
+
 # The test suite will fail without the "required" subset.
 BDEPEND="test? ( ${REQUIRED_PKGS} )"
 
@@ -37,7 +60,7 @@ RDEPEND="${DEPEND}"
 
 # If you _really_ want to install GAP without the set of required
 # packages, use package.provided.
-PDEPEND="${REQUIRED_PKGS}"
+PDEPEND="${REQUIRED_PKGS} !minimal? ( ${AUTOLOADED_PKGS} )"
 
 pkg_setup() {
 	if use valgrind; then

sci-mathematics/gap/metadata.xml

@@ -28,6 +28,11 @@
   </longdescription>
   <use>
     <flag name="memcheck">Enable memory checking</flag>
+    <flag name="minimal">
+      Install only the GAP packages that are strictly required for GAP
+      to run. GAP will complain about the others unless you either start
+      it with the "-A" flag or set "AutoloadPackages" in your gap.ini.
+    </flag>
   </use>
   <upstream>
     <remote-id type="github">gap-system/gap</remote-id>