meson.build: generate version.h in include/mpd/

This fixes a "version.h" conflict when used as a Meson subproject:
when the parent project also generates a "version.h", it is not clear
which one will be included.  We solve this by requiring the "mpd/"
prefix for libmpdclient.

See MusicPlayerDaemon/MPD#1927

NEWS

@@ -1,5 +1,6 @@
 libmpdclient 2.22 (not yet released)
 * drop the unmaintained Vala bindings
+* fix "version.h" conflicts when used as a Meson subproject
 
 libmpdclient 2.21 (2023/12/20)
 * meson.build: allow using as a Meson subproject

include/mpd/client.h

@@ -81,7 +81,10 @@
 #include "stats.h"
 #include "status.h"
 #include "sticker.h"
-#include "version.h"
+
+/* this is a generated header and may be installed in a different
+   filesystem tree, therefore we can't use just "version.h" */
+#include <mpd/version.h>
 
 // IWYU pragma: end_exports
 

include/mpd/meson.build

@@ -1,3 +1,13 @@
+version_conf = configuration_data()
+version_conf.set('MAJOR_VERSION', splitted_version[0])
+version_conf.set('MINOR_VERSION', splitted_version[1])
+if splitted_version.length() >= 3
+  version_conf.set('PATCH_VERSION', splitted_version[2])
+else
+  version_conf.set('PATCH_VERSION', '0')
+endif
+version_h = configure_file(input: 'version.h.in', output: 'version.h', configuration: version_conf)
+
 install_headers(
   'async.h',
   'audio_format.h',

meson.build

@@ -35,16 +35,7 @@ endif
 
 configure_file(output: 'config.h', configuration: conf)
 
-version_conf = configuration_data()
 splitted_version = meson.project_version().split('.')
-version_conf.set('MAJOR_VERSION', splitted_version[0])
-version_conf.set('MINOR_VERSION', splitted_version[1])
-if splitted_version.length() >= 3
-  version_conf.set('PATCH_VERSION', splitted_version[2])
-else
-  version_conf.set('PATCH_VERSION', '0')
-endif
-version_h = configure_file(input: 'include/mpd/version.h.in', output: 'version.h', configuration: version_conf)
 
 common_cflags = [
 ]
@@ -99,9 +90,6 @@ inc = include_directories(
 
 public_inc = include_directories(
   'include',
-
-  # for the generated version.h
-  '.',
 )
 
 subdir('include/mpd')