Escape TTY in systemd service (closes #889) (#890)

## What are the changes about?

* fix templated systemd dependencies: %I -> %i
* amend systemd-specific documentation in readme with section specific to systemd-logind / autovt

## What existing issue does this resolve?

[issue #889](https://codeberg.org/fairyglade/ly/issues/889)

## Pre-requisites

- [x] I have tested & confirmed the changes work locally

Reviewed-on: https://codeberg.org/fairyglade/ly/pulls/890
Reviewed-by: AnErrupTion <anerruption@disroot.org>
Co-authored-by: qbe <public.github.c@hannen.at>
Co-committed-by: qbe <public.github.c@hannen.at>

build.zig

@@ -23,7 +23,7 @@ comptime {
     }
 }
 
-const ly_version = std.SemanticVersion{ .major = 1, .minor = 3, .patch = 0 };
+const ly_version = std.SemanticVersion{ .major = 1, .minor = 4, .patch = 0 };
 
 var dest_directory: []const u8 = undefined;
 var config_directory: []const u8 = undefined;

build.zig.zon

@@ -1,6 +1,6 @@
 .{
     .name = .ly,
-    .version = "1.3.0",
+    .version = "1.4.0",
     .fingerprint = 0xa148ffcc5dc2cb59,
     .minimum_zig_version = "0.15.0",
     .dependencies = .{

readme.md

@@ -121,9 +121,15 @@ that Ly will run on, otherwise bad things will happen. For example, to disable `
 # systemctl disable getty@tty2.service
 ```
 
-You can change the TTY Ly will run on by editing the corresponding
-service file for your platform, or on systemd, by enabling the service on
-different TTYs, as is done above.
+On platforms that use systemd-logind to dynamically start `autovt@.service` instances when the switch to a new tty occurs, any ly instances for ttys *except the default tty* need to be enabled using a different mechanism: To autostart ly on switch to `tty2`, do not enable any `ly` unit directly, instead symlink `autovt@tty2.service` to `ly@tty2.service` within `/usr/lib/systemd/system/` (analogous for every other tty you want to enable ly on).
+
+The target of the symlink, `ly@ttyN.service`, does not actually exist, but systemd nevertheless recognizes that the instanciation of `autovt@.service` with `%I` equal to `ttyN` now points to an instanciation of `ly@.service` with `%I` set to `ttyN`.
+
+Compare to `man 5 logind.conf`, especially regarding the `NAutoVTs=` and `ReserveVT=` parameters.
+
+
+On non-systemd systems, you can change the TTY Ly will run on by editing the corresponding
+service file for your platform.
 
 ### OpenRC
 

res/ly@.service

@@ -1,8 +1,8 @@
 [Unit]
 Description=TUI display manager
 After=systemd-user-sessions.service plymouth-quit-wait.service
-After=getty@%I.service
-Conflicts=getty@%I.service
+After=getty@%i.service
+Conflicts=getty@%i.service
 
 [Service]
 Type=idle

src/tui/components/Session.zig

@@ -41,15 +41,19 @@ pub fn addEnvironment(self: *Session, environment: Environment) !void {
     const env = Env{ .environment = environment, .index = self.label.list.items.len };
 
     try self.label.addItem(env);
-    sessionChanged(env, self.user_list);
+    addedSession(env, self.user_list);
+}
+
+fn addedSession(env: Env, user_list: *UserList) void {
+    const user = user_list.label.list.items[user_list.label.current];
+    if (!user.first_run) return;
+
+    user.session_index.* = env.index;
 }
 
 fn sessionChanged(env: Env, maybe_user_list: ?*UserList) void {
     if (maybe_user_list) |user_list| {
-        const user = user_list.label.list.items[user_list.label.current];
-        if (!user.first_run) return;
-
-        user.session_index.* = env.index;
+        user_list.label.list.items[user_list.label.current].session_index.* = env.index;
     }
 }