tools: add v retry apt update, for more robust CI jobs

cmd/tools/vretry.v

@@ -0,0 +1,57 @@
+import os
+import time
+import flag
+
+struct Context {
+mut:
+	show_help bool
+	timeout   time.Duration
+	delay     time.Duration
+	retries   int
+}
+
+fn main() {
+	mut context := Context{}
+	mut fp := flag.new_flag_parser(os.args#[1..])
+	fp.application('v retry')
+	fp.version('0.0.1')
+	fp.description('Run the command CMD in a loop, untill it succeeds, or until a predetermined amount of seconds pass.')
+	fp.arguments_description('CMD')
+	fp.skip_executable()
+	fp.limit_free_args_to_at_least(1)!
+	context.show_help = fp.bool('help', `h`, false, 'Show this help screen.')
+	context.timeout = fp.float('timeout', `t`, 300.0, 'Timeout in seconds. Default: 300.0 seconds.') * time.second
+	context.delay = fp.float('delay', `d`, 1.0, 'Delay between each retry in seconds. Default: 1.0 second.') * time.second
+	context.retries = fp.int('retries', `r`, 999_999_999, 'Maximum number of retries. Default: 999_999_999.')
+	if context.show_help {
+		println(fp.usage())
+		exit(0)
+	}
+	command_args := fp.finalize() or {
+		eprintln('Error: ${err}')
+		exit(1)
+	}
+	cmd := command_args.join(' ')
+
+	spawn fn (context Context) {
+		time.sleep(context.timeout)
+		eprintln('error: exceeded maximum timeout (${context.timeout.seconds()}s)!')
+		exit(1)
+	}(context)
+
+	mut res := 0
+	mut i := 0
+	for {
+		i++
+		res = os.system(cmd)
+		if res == 0 {
+			break
+		}
+		if i >= context.retries {
+			eprintln('error: exceeded maximum number of retries (${context.retries})!')
+			exit(res)
+		}
+		time.sleep(context.delay)
+	}
+	exit(res)
+}

cmd/v/v.v

@@ -31,6 +31,7 @@ const external_tools = [
 	'missdoc',
 	'repl',
 	'repeat',
+	'retry',
 	'self',
 	'setup-freetype',
 	'shader',