[dconf/wip/jtojnar/bash-completion-prefix] build: Install bash-completion relative to datadir

[Jan Tojnar <jtojnar src gnome org>]

commit ba4abea9605fde709fd700383791ca760b24f8b4
Author: Jan Tojnar <jtojnar gmail com>
Date:   Thu Apr 16 11:21:06 2020 +0200

    build: Install bash-completion relative to datadir
    
    Since bash-completion 2.9, it was no longer possible to override
    the completionsdir through prefix. [1] In 2.10, the overridability
    was re-estabilished but this time through datadir variable. [2]
    
    This should not really matter except for developers installing the project
    into a custom prefix or distros using per-package prefixes like NixOS.
    
    [1]: https://github.com/scop/bash-completion/commit/81ba2c7e7dfbaefbafa1e8615727c9612e5fb314
    [2]: https://github.com/scop/bash-completion/pull/344
    
    Co-Authored-By: Iñigo Martínez <inigomartinez gmail com>

 meson.build | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/meson.build b/meson.build
index 6620112..b7114bf 100644
--- a/meson.build
+++ b/meson.build
@@ -50,8 +50,12 @@ dbus_session_service_dir = dependency('dbus-1').get_pkgconfig_variable('session_
 
 enable_bash_completion = get_option('bash_completion')
 if enable_bash_completion
-  # FIXME: the `.pc` file is wrong because `completionsdir` should be relative to `datadir`, not `prefix`
-  completions_dir = dependency('bash-completion').get_pkgconfig_variable('completionsdir', define_variable: 
['prefix', dconf_prefix])
+  bash_completion_dep = dependency('bash-completion')
+  completions_dir = bash_completion_dep.get_pkgconfig_variable(
+    'completionsdir',
+    # bash-completion 2.10 changed the substitutions
+    define_variable: bash_completion_dep.version().version_compare('>= 2.10') ? ['datadir', dconf_datadir] : 
['prefix', dconf_prefix],
+  )
 endif
 
 configure_file(