Change internal getopts so --a=b=c acts like --a b=c rather than --a b.

This is an adaption of

 rust-lang/getopts@8ec916b

including its unit test.

Author: pnkfelix

src/libgetopts/lib.rs

@@ -598,7 +598,7 @@ pub fn getopts(args: &[String], optgrps: &[OptGroup]) -> Result {
             let mut i_arg = None;
             if cur.as_bytes()[1] == b'-' {
                 let tail = &cur[2..curlen];
-                let tail_eq: Vec<&str> = tail.split('=').collect();
+                let tail_eq: Vec<&str> = tail.splitn(2, '=').collect();
                 if tail_eq.len() <= 1 {
                     names = vec![Long(tail.to_owned())];
                 } else {
@@ -1626,4 +1626,18 @@ Options:
         debug!("generated: <<{}>>", generated_usage);
         assert_eq!(generated_usage, expected);
     }
+
+    #[test]
+    fn test_args_with_equals() {
+        let args = vec!("--one".to_string(), "A=B".to_string(),
+                        "--two=C=D".to_string());
+        let opts = vec![optopt("o", "one", "One", "INFO"),
+                        optopt("t", "two", "Two", "INFO")];
+        let matches = &match getopts(&args, &opts) {
+            result::Result::Ok(m) => m,
+            result::Result::Err(e) => panic!("{}", e)
+        };
+        assert_eq!(matches.opts_str(&["o".to_string()]).unwrap(), "A=B");
+        assert_eq!(matches.opts_str(&["t".to_string()]).unwrap(), "C=D");
+    }
 }