From 7da78a3102dce586b571a3ea5719a518c1dc42b1 Mon Sep 17 00:00:00 2001
From: Max Gautier <mg@max.gautier.name>
Date: Wed, 28 Feb 2024 21:19:59 +0100
Subject: [PATCH] Use systemd-tmpfiles for var dirs when on systemd

Putting packages files in /var prevent makes new install start with an
already populated /var, which prevent taking advantage of the systemd
provided tmpfiles.d/var.conf, which notably has this line:
q /var 0755 - - -
-> on supported filesystems (currently that means btrfs), this creates
/var as a subvolume, which has the benefit of excluding it from /
snapshots.

On non-systemd system, the `meson install` behavior stays the same,
/var/lib/pacman and /var/cache/pacman/pkg are included in DESTDIR.

Signed-off-by: Max Gautier <mg@max.gautier.name>
---
 meson.build   | 17 ++++++++++++++---
 tmpfiles.conf |  4 ++++
 2 files changed, 18 insertions(+), 3 deletions(-)
 create mode 100644 tmpfiles.conf

diff --git a/meson.build b/meson.build
index 84154bc2..c3779a47 100644
--- a/meson.build
+++ b/meson.build
@@ -445,9 +445,20 @@ install_data(
   'proto/proto.install',
   install_dir : join_paths(DATAROOTDIR, 'pacman'))
 
-foreach path : [
-	join_paths(LOCALSTATEDIR, 'lib/pacman/'),
-	join_paths(LOCALSTATEDIR, 'cache/pacman/pkg/'),
+systemd = dependency('systemd', required: false)
+if systemd.found()
+	install_data('tmpfiles.conf',
+				rename: 'pacman.conf',
+				install_dir: systemd.get_variable(pkgconfig: 'tmpfilesdir'))
+	var_paths = []
+else
+	var_paths = [
+		join_paths(LOCALSTATEDIR, 'lib/pacman/'),
+		join_paths(LOCALSTATEDIR, 'cache/pacman/pkg/'),
+		]
+endif
+
+foreach path : var_paths + [
 	join_paths(DATAROOTDIR, 'makepkg-template/'),
 	join_paths(DATAROOTDIR, 'libalpm/hooks/'),
 	]
diff --git a/tmpfiles.conf b/tmpfiles.conf
new file mode 100644
index 00000000..bdad4fab
--- /dev/null
+++ b/tmpfiles.conf
@@ -0,0 +1,4 @@
+# Setup pacman data and cache directories
+
+d %S/pacman
+d %C/pacman/pkg