[mutter] build: Bump API version automatically each development cycle

[Florian Müllner <fmuellner src gnome org>]

commit 92868182c9b012523d1a159c98a2cfc8b7b9c8f0
Author: Florian Müllner <fmuellner gnome org>
Date:   Tue Jul 23 20:26:14 2019 +0200

    build: Bump API version automatically each development cycle
    
    Since the API version was added, we've bumped it at some point late-ish in
    the cycle when enough changes had accumulated (but way after the first ABI
    break). Automate that process by computing the API version automatically
    from the project version:
    With this commit, the new API version will be 5 for the remaining 3.33.x
    releases and all 3.34.x stable versions; 3.35.1 will then bump it to 6 and
    so forth.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/696

 meson.build | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index 6b8275662..7e774c4d9 100644
--- a/meson.build
+++ b/meson.build
@@ -6,7 +6,12 @@ project('mutter', 'c',
 
 mutter_plugin_api_version = '3'
 
-libmutter_api_version = '4'
+split_version = meson.project_version().split('.')
+
+# Automatically increase API version each development cycle,
+# starting with 0 in 3.23.x
+api_version = (split_version[1].to_int() - 23) / 2
+libmutter_api_version = '@0@'.format(api_version)
 
 # generic version requirements
 fribidi_req = '>= 1.0.0'