meson: make docdir configurable

The debian package wants to install docs to $datadir/doc/i3-wm.

related to #4086

debian/rules

@@ -14,8 +14,8 @@ override_dh_auto_test:
 	# TODO: enable tests
 
 override_dh_auto_configure:
-	# The default is /usr/share/doc/i3
-	dh_auto_configure -- --docdir=/usr/share/doc/i3-wm
+	# Set -Ddocdir; the default is /usr/share/doc/i3
+	dh_auto_configure -- -Ddocdir=/usr/share/doc/i3-wm
 
 override_dh_builddeb:
 	# bintray does not support xz currently.

meson.build

@@ -71,6 +71,11 @@ config_h = declare_dependency(
 # docs generation
 ################################################################################
 
+docdir = get_option('docdir')
+if docdir == ''
+  docdir = join_paths(get_option('datadir'), 'doc', 'i3')
+endif
+
 if get_option('docs')
   asciidoc = find_program('asciidoc')
   doc_toc_inputs = [
@@ -96,7 +101,7 @@ if get_option('docs')
         '@INPUT@',
       ],
       install: true,
-      install_dir: join_paths(get_option('datadir'), 'doc', 'i3'),
+      install_dir: docdir,
     )
   endforeach
 
@@ -115,7 +120,7 @@ if get_option('docs')
         '@INPUT@',
       ],
       install: true,
-      install_dir: join_paths(get_option('datadir'), 'doc', 'i3'),
+      install_dir: docdir,
     )
   endforeach
 endif

meson_options.txt

@@ -5,3 +5,6 @@ option('docs', type: 'boolean', value: false,
 
 option('mans', type: 'boolean', value: false,
        description: 'Build manpages from source (release tarballs contain a generated copy)')
+
+option('docdir', type: 'string', value: '',
+       description: 'documentation directory (default: $datadir/docs/i3)')