Added note about time formatting

This closes #2312

License: MIT
Signed-off-by: Richard Littauer <richard.littauer@gmail.com>

core/commands/publish.go

@@ -51,7 +51,11 @@ Publish an <ipfs-path> to another public key (not implemented):
 	},
 	Options: []cmds.Option{
 		cmds.BoolOption("resolve", "Resolve given path before publishing (default=true)."),
-		cmds.StringOption("lifetime", "t", "Time duration that the record will be valid for (default: 24hrs)."),
+		cmds.StringOption("lifetime", "t", `Time duration that the record will be valid for. Default: 24h.
+
+    This accepts durations such as "300s", "1.5h" or "2h45m". Valid time units are
+    "ns", "us" (or "µs"), "ms", "s", "m", "h".
+		`),
 		cmds.StringOption("ttl", "Time duration this record should be cached for (caution: experimental)."),
 	},
 	Run: func(req cmds.Request, res cmds.Response) {