build: include documentation in meson dist

Previously, the tarball generated by `meson dist` did not contain the
autogenerated documentation due to the way meson works (packaging the
latest revision control commit). This introduces a dist script which
builds & copies the generated documentation into the distribution
tarball.

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1811

meson.build

@@ -978,9 +978,13 @@ endif
 
 if enable_docs
   assert(enable_introspection, '-Ddocs=true requires -Dintrospection=true')
-  assert(meson.version().version_compare('>= 0.46.0'), '-Ddocs requires meson >= 0.46')
+  assert(meson.version().version_compare('>= 0.49.0'), '-Ddocs requires meson >= 0.49')
   subdir('man')
   subdir('docs')
+  meson.add_dist_script(
+    'tools/meson-dist-data.sh',
+    '--build-root', build_root
+  )
 endif
 
 configure_file(

tools/meson-dist-data.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+set -e
+
+ensure_var_path() {
+  if [ "${!1}" = "" ]; then
+      echo "$0: Required variable $1 is not set, aborting" >&2
+      exit 1
+  fi
+
+  if [ ! -d "${!1}" ]; then
+      echo "$0: Path '${!1}' in $1 does not exist or is not directory, aborting" >&2
+      exit 1
+  fi
+}
+
+copy_from_build() {
+    cp -Tr "$MESON_BUILD_ROOT/$1" "$MESON_DIST_ROOT/$1"
+}
+
+if [ "$MESON_BUILD_ROOT" = "" ]; then
+    if [ "$1" = "--build-root" ]; then
+        MESON_BUILD_ROOT="$2"
+    fi
+fi
+
+ensure_var_path "MESON_DIST_ROOT"
+ensure_var_path "MESON_BUILD_ROOT"
+ensure_var_path "MESON_SOURCE_ROOT"
+
+ninja -C "$MESON_BUILD_ROOT" all libnm-doc NetworkManager-doc
+
+mkdir -p "$MESON_DIST_ROOT/docs/"
+copy_from_build /docs/api/
+copy_from_build /docs/libnm/
+copy_from_build /man/