tools: add v time, to measure command execution time, in a cross platform way, without relying on other external tools

cmd/tools/vtime.v

@@ -0,0 +1,39 @@
+import os
+import term
+import time
+import flag
+
+struct Context {
+mut:
+	show_help     bool
+	cmd_line_opts []string
+}
+
+fn main() {
+	mut ctx := Context{}
+	args := arguments()
+	mut fp := flag.new_flag_parser(args#[1..])
+	fp.application('v time')
+	fp.version('0.0.1')
+	fp.description('Start a command, and report how much time it took to run, and what its exit code was.')
+	fp.arguments_description('CMD [ARGS]')
+	fp.skip_executable()
+	fp.limit_free_args_to_at_least(1)!
+	ctx.show_help = fp.bool('help', `h`, false, 'Show this help screen.')
+	if ctx.show_help {
+		println(fp.usage())
+		exit(0)
+	}
+	ctx.cmd_line_opts = fp.finalize() or {
+		eprintln('Error: ${err}')
+		exit(1)
+	}
+	cmd := ctx.cmd_line_opts.join(' ')
+	sw := time.new_stopwatch()
+	ecode := os.system(cmd)
+	elapsed := sw.elapsed()
+	stook_time := '${f64(elapsed.microseconds()) / 1000.0:8.3f} ms'
+	eprintln('> ${term.ecolorize(term.bright_yellow, stook_time)}. Exit code: ${ecode:3}. Command: ${term.ecolorize(term.green,
+		cmd)}')
+	exit(ecode)
+}

cmd/v/v.v

@@ -47,6 +47,7 @@ const external_tools = [
 	'test-fmt',
 	'test-parser',
 	'test-self',
+	'time',
 	'tracev',
 	'up',
 	'vet',

vlib/v/help/other/time.txt

@@ -0,0 +1,10 @@
+v time 0.0.1
+-----------------------------------------------
+Usage: v time [options] CMD [ARGS]
+
+Description: Start a command, and report how much time it took to run, and what its exit code was.
+
+The arguments should be at least 1 in number.
+
+Options:
+  -h, --help                Show this help screen.