Clarify [doc].browser docs, document PathAndArgs better

Author: lf-

src/doc/src/reference/config.md

@@ -195,6 +195,20 @@ runner = "foo"  # Searches `PATH` for `foo`.
 directory = "vendor"
 ```
 
+### Executable paths with arguments
+
+Some Cargo commands invoke external programs, which can be configured as a path
+and some number of arguments.
+
+The value may be an array of strings like `['/path/to/program', 'somearg']` or
+a space-separated string like `'/path/to/program somearg'`. If the path to the
+executable contains a space, the list form must be used.
+
+If Cargo is passing other arguments to the program such as a path to open or
+run, they will be passed after the last specified argument in the value of an
+option of this format. If the specified program does not have path separators,
+Cargo will search `PATH` for its executable.
+
 ### Credentials
 
 Configuration values with sensitive information are stored in the
@@ -406,6 +420,10 @@ The `[doc]` table defines options for the [`cargo doc`] command.
 
 ##### `doc.browser`
 
+* Type: string or array of strings ([program path and args])
+* Default: `BROWSER` environment variable, or, if that is missing,
+  opening the link in a system specific way
+
 This option sets the browser to be used by [`cargo doc`], overriding the
 `BROWSER` environment variable when opening documentation with the `--open`
 option.
@@ -837,7 +855,7 @@ Specifies the linker which is passed to `rustc` (via [`-C linker`]) when the
 `<triple>` is being compiled for. By default, the linker is not overridden.
 
 ##### `target.<triple>.runner`
-* Type: string or array of strings (program path and args)
+* Type: string or array of strings ([program path and args])
 * Default: none
 * Environment: `CARGO_TARGET_<triple>_RUNNER`
 
@@ -846,12 +864,6 @@ executed by invoking the specified runner with the actual executable passed as
 an argument. This applies to [`cargo run`], [`cargo test`] and [`cargo bench`]
 commands. By default, compiled executables are executed directly.
 
-The value may be an array of strings like `['/path/to/program', 'somearg']` or
-a space-separated string like `'/path/to/program somearg'`. The arguments will
-be passed to the runner with the executable to run as the last argument. If
-the runner program does not have path separators, it will search `PATH` for
-the runner executable.
-
 ##### `target.<cfg>.runner`
 
 This is similar to the [target runner](#targettriplerunner), but using
@@ -958,6 +970,7 @@ Sets the width for progress bar.
 [toml]: https://toml.io/
 [incremental compilation]: profiles.md#incremental
 [profile]: profiles.md
+[program path with args]: #executable-paths-with-arguments
 [libcurl format]: https://ec.haxx.se/usingcurl-proxies.html
 [source replacement]: source-replacement.md
 [revision]: https://git-scm.com/docs/gitrevisions