Rename extra-args to extra-arg since it only adds 1 argument.

This is a backwards incompatible change, but it makes it much clearer that no
string processing is happening.

Author: ltratt

README.md

@@ -143,9 +143,9 @@ Each test command must define at least one sub-test:
 Test commands can alter the general command by specifying zero or more of the
 following:
 
-  * `extra-args: <string>` specifies a string which will be passed as an
+  * `extra-arg: <string>` specifies a string which will be passed as an
     additional command-line argument to the command (in addition to those
-    specified by the `test_cmds` function). Multiple `extra-args` can be
+    specified by the `test_cmds` function). Multiple `extra-arg`s can be
     specified, each adding an additional command-line argument.
  * `stdin: <string>`, text to be passed to the command's `stdin`. If the
    command exits without having consumed all of `<string>`, an error will be

examples/rust_lang_tester/lang_tests/custom_cla.rs

@@ -1,6 +1,6 @@
 // Run-time:
-//   extra-args: 1
-//   extra-args: 2 3
+//   extra-arg: 1
+//   extra-arg: 2 3
 
 use std::env;
 

src/lib.rs

@@ -140,10 +140,10 @@
 //!
 //! Test commands can alter the general command by specifying zero or more of the following:
 //!
-//!   * `extra-args: <string>` specifies a string which will be passed as an additional
+//!   * `extra-arg: <string>` specifies a string which will be passed as an additional
 //!     command-line argument to the command (in addition to those specified by the `test_cmds`
-//!     function). Multiple `extra-args` can be specified, each adding an additional command-line
-//!     argument.
+//!     function). `extra-arg` can be specified multiple times, each adding an additional
+//!     command-line argument.
 //!   * stdin: <string>`, text to be passed to the command's `stdin`. If the command exits without
 //!     having consumed all of `<string>`, an error will be raised. Note, though, that operating
 //!     system file buffers can mean that the command *appears* to have consumed all of `<string>`

src/parser.rs

@@ -49,7 +49,7 @@ pub(crate) fn parse_tests(test_str: &str) -> Tests {
                     let (end_line_off, key, val) = key_multiline_val(&lines, line_off, sub_indent);
                     line_off = end_line_off;
                     match key {
-                        "extra-args" => {
+                        "extra-arg" => {
                             let val_str = val.join("\n");
                             testcmd.args.push(val_str);
                         }