adds parsing timestamps with alternate precisions (including new option --millis)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "utcnow"
-version = "1.2.0"
+version = "1.3.0"
 authors = ["Jonathan Strong <jonathan.strong@gmail.com>"]
 edition = "2018"
 

src/main.rs

@@ -52,8 +52,14 @@ fn main() {
             .help("display unix timestamp in seconds, instead of default nanoseconds")
             .long("seconds")
             .short("s")
-            .requires("unix")
-            .conflicts_with_all(&["rfc2822", "timespec"])
+            .conflicts_with_all(&["rfc2822", "timespec", "millis"])
+            .required(false)
+            .takes_value(false))
+        .arg(clap::Arg::with_name("millis")
+            .help("display unix timestamp in milliseconds, instead of default nanoseconds")
+            .long("millis")
+            .short("m")
+            .conflicts_with_all(&["rfc2822", "timespec", "seconds"])
             .required(false)
             .takes_value(false))
         .arg(clap::Arg::with_name("timespec")
@@ -70,13 +76,17 @@ fn main() {
             .required(false))
         .arg(clap::Arg::with_name("unix-to-rfc3339")
             .long("unix-to-rfc3339")
+            .short("R")
             .alias("unix-to-utc")
-            .help("convert integer unix timestamp (nanoseconds precision) to datetime in rfc3339 format")
+            .help("convert integer unix timestamp (nanoseconds precision) to datetime \
+                   in rfc3339 format. combine with --seconds or --millis to parse a
+                   seconds timestamp with alternate precison")
             .takes_value(true)
             .required(false)
-            .conflicts_with_all(&["unix", "seconds"]))
+            .conflicts_with_all(&["unix"]))
         .arg(clap::Arg::with_name("rfc3339-to-unix")
             .long("rfc3339-to-unix")
+            .short("U")
             .alias("utc-to-unix")
             .help("parse rfc3339 timestamp and display it as a unix timestamp")
             .takes_value(true)
@@ -89,6 +99,15 @@ fn main() {
 
         if let Some(ts_str) = args.value_of("unix-to-rfc3339") {                        // either parse --unix-to-rfc3339 input
             match u64::from_str(ts_str) {
+
+                // check alternate precisions --seconds or --millis
+
+                Ok(seconds) if args.is_present("seconds") => nanos_to_timespec(seconds * ONE_SECOND),
+                
+                Ok(millis) if args.is_present("millis") => nanos_to_timespec(millis * 1_000_000),
+
+                // otherwise go with default nanos
+
                 Ok(nanos) => nanos_to_timespec(nanos),
 
                 Err(e) => {
@@ -124,7 +143,8 @@ fn main() {
 
         if args.is_present("seconds") {                                                 // unix seconds
             print!("{}{}", sec, endline);
-
+        } else if args.is_present("millis") {                                           // unix millis
+            print!("{}{}", timespec_to_nanos(sec, nsec) / 1_000_000, endline);
         } else {                                                                        // unix nanos
             print!("{}{}", timespec_to_nanos(sec, nsec), endline);
         }