common: define meta-packages with metapackage=yes

Overloading `build_style` for meta-packages has always felt very hacky,
and it prevents having the main package be a meta-package (with non-meta
subpackages) and using a `build_style` at the same time (example of
trying to hack around that: 62c0c08e18).
It also can create confusion about how subpackages work if you can
define a `build_style` there (but only `meta`).

This makes using `build_style=meta` an error at the package and subpackage
level, and replaces it with a new variable (`metapackage=yes`).

A pkglint for non-empty meta-packages is also added.

Manual.md

@@ -691,6 +691,9 @@ redistribution.
 to override the guessed list. Only use this if a specific order of subpackages is required,
 otherwise the default would work in most cases.
 
+- `metapackage` If set to `yes`, the package must be an empty meta-package, i.e. a package that
+only depends on other packages.
+
 - `broken` If set, building the package won't be allowed because its state is currently broken.
 This should be set to a string describing why it is broken, or a link to a buildlog demonstrating the failure.
 
@@ -1011,11 +1014,6 @@ information can be found in the `go.mod` file for modern Go projects.
 It's expected that the distfile contains the package, but dependencies
 will be downloaded with `go get`.
 
-- `meta` For `meta-packages`, i.e packages that only install local files or simply
-depend on additional packages. This build style does not install
-dependencies to the root directory, and only checks if a binary package is
-available in repositories.
-
 - `R-cran` For packages that are available on The Comprehensive R Archive
 Network (CRAN). The build style requires the `pkgname` to start with
 `R-cran-` and any dashes (`-`) in the CRAN-given version to be replaced

common/build-style/meta.sh

@@ -1,9 +0,0 @@
-# meta pkg build style; do nothing.
-
-do_fetch() {
-	:
-}
-
-do_install() {
-	:
-}

common/environment/setup-subpkg/subpkg.sh

@@ -3,7 +3,7 @@
 
 ## VARIABLES
 unset -v conf_files mutable_files preserve triggers alternatives
-unset -v depends run_depends replaces provides conflicts tags
+unset -v depends run_depends replaces provides conflicts tags metapackage
 
 # hooks/post-install/03-strip-and-debug-pkgs
 unset -v nostrip nostrip_files

common/hooks/pre-pkg/99-pkglint.sh

@@ -63,9 +63,13 @@ hook() {
 		esac
 	done
 
-	# Forbid empty packages unless build_style=meta or it is 32bit devel package
-	if [ "$build_style" != meta ] && [ "$emptypkg" != no ] && [[ ${pkgname} != *-devel-32bit ]]; then
-		msg_red "${pkgver}: PKGDESTDIR is empty and build_style != meta\n"
+	# Forbid empty packages unless metapackage=yes or it is 32bit devel package
+	if [ "$metapackage" != yes ] && [ "$emptypkg" != no ] && [[ ${pkgname} != *-devel-32bit ]]; then
+		msg_red "${pkgver}: PKGDESTDIR is empty and metapackage != yes\n"
+		error=1
+	fi
+	if [ "$metapackage" = yes ] && [ "$emptypkg" = no ]; then
+		msg_red "${pkgver}: PKGDESTDIR of meta package is not empty\n"
 		error=1
 	fi
 

common/xbps-src/libexec/xbps-src-doinstall.sh

@@ -34,7 +34,13 @@ if [ "$SUBPKG_MODE"  = "no" ]; then
     if [ ! -f $XBPS_INSTALL_DONE ] || [ -f $XBPS_INSTALL_DONE -a -n "$XBPS_BUILD_FORCEMODE" ]; then
         mkdir -p $XBPS_DESTDIR/$XBPS_CROSS_TRIPLET/$pkgname-$version
 
-        run_step install "" skip
+        if [ "$metapackage" = yes ]; then
+            optional="optional"
+        else
+            optional=""
+        fi
+
+        run_step install "$optional" skip
 
         touch -f $XBPS_INSTALL_DONE
     fi
@@ -54,6 +60,10 @@ if [ ! -f $XBPS_SUBPKG_INSTALL_DONE -o -n "$XBPS_BUILD_FORCEMODE" ]; then
         ${PKGNAME}_package
         pkgname=$PKGNAME
 
+        if [ "$build_style" = meta ]; then
+            msg_error "$pkgver: build_style=meta is deprecated, replace with metapackage=yes\n"
+        fi
+
         source_file $XBPS_COMMONDIR/environment/build-style/${build_style}.sh
 
         install -d $PKGDESTDIR

common/xbps-src/shutils/common.sh

@@ -523,12 +523,14 @@ setup_pkg() {
 
     pkgver="${pkg}-${version}_${revision}"
 
-    # If build_style() unset, a do_install() function must be defined.
+    # If build_style is unset, a do_install() function must be defined.
     if [ -z "$build_style" ]; then
         # Check that at least do_install() is defined.
-        if ! declare -f do_install >/dev/null; then
+        if [ "$metapackage" != yes ] && ! declare -f do_install >/dev/null; then
             msg_error "$pkgver: missing do_install() function!\n"
         fi
+    elif [ "$build_style" = meta ]; then
+        msg_error "$pkgver: build_style=meta is deprecated, replace with metapackage=yes\n"
     fi
 
     for x in ${hostmakedepends} ${makedepends} ${checkdepends}; do