code review 3071041: flag: handle multiple calls to flag.Parse

flag: handle multiple calls to flag.Parse

[rsc, 2010-12-06 19:22:32]

Hello golang-dev@googlegroups.com,

I'd like you to review this change.

[rsc1, 2010-12-06 19:27:47]

R=r 

This change keeps flag.Parse from crashing if called multiple times.
It also lets one do things like

flag.Parse()
switch flag.Arg(0) {
case "cmd1":
    ... add more flags
case "cmd2":
    ... add more flags
}
os.Args = flag.Args()
flag.Parse()

to implement the common subcommand 
command line parsing found in tools like
Mercurial.  I'm not sure if that's a good thing,
but not crashing certainly is.

[r, 2010-12-06 19:33:09]

looks good but wants a test if feasible and maybe a sentence of new package
documentation

[rsc, 2010-12-07 16:50:09]

Hello r (cc: golang-dev@googlegroups.com),

Please take another look.

[r, 2010-12-07 16:57:19]

LGTM

[rsc, 2010-12-07 18:19:03]

*** Submitted as cc69ceb37529 ***

flag: handle multiple calls to flag.Parse

R=r
CC=golang-dev
http://codereview.appspot.com/3071041