feat: order/delay in service files, enable cmd, --all on unit commands

- install/uninstall/start/stop/enable take <name> or --all; *all kept as shortcuts
- add enable (enable at boot + start); startall no longer enables
- order/delay resolved by config.ResolveOrder and written into systemd,
  OpenRC and runit service files (After=/sleep), so they apply at boot
- install --all stops and disables units before removing their files
- update regenerates all installed, enabled units and removes disabled ones
- edit creates the config dir; docs and man page updated
- tests: fake Init for cmd, ResolveOrder, backend ordering output

runit/runit.go

@@ -125,7 +125,7 @@ func (b Backend) files(u config.Unit, prefix, suffix string) ([]file, error) {
 
 	header := "#!/bin/sh\n# " + b.ServiceName(u, prefix, suffix) + " — generated by unitdore, do not edit manually\n"
 
-	run := header + "exec 2>&1\n" + preamble(user, spec.WorkingDir)
+	run := header + "exec 2>&1\n" + b.waitFor(u, prefix, suffix) + preamble(user, spec.WorkingDir)
 	if spec.Type == service.TypeOneshot {
 		// Run once, then stay up (like RemainAfterExit) until stopped
 		run += asUser(user, start) + " || exit 1\nexec tail -f /dev/null\n"
@@ -140,6 +140,24 @@ func (b Backend) files(u config.Unit, prefix, suffix string) ([]file, error) {
 	return files, nil
 }
 
+// predecessorWait is how long run waits for each unit of the previous group.
+const predecessorWait = 30
+
+// waitFor holds the service until the previous order group is up, then sleeps
+// the unit's delay. `sv check` never starts a service, and returns at once for
+// one that is down or not installed.
+func (b Backend) waitFor(u config.Unit, prefix, suffix string) string {
+	var s string
+	for _, n := range u.After {
+		link := b.link(config.Unit{Name: n}, prefix, suffix)
+		s += fmt.Sprintf("sv -w %d check %s >/dev/null 2>&1 || true\n", predecessorWait, service.ShellQuote(link))
+	}
+	if secs := int((u.StartDelay + time.Second - 1) / time.Second); secs > 0 {
+		s += fmt.Sprintf("sleep %d\n", secs)
+	}
+	return s
+}
+
 // preamble prepares the environment: working dir and rootless user runtime.
 func preamble(user *service.UserEnv, workDir string) string {
 	var s string