Fix documentation related to 'command-switch-alist'.

While there, add a unit test to verify the behavior.

* doc/lispref/os.texi (Command-Line Arguments): Fix documentation: the
option string in 'command-switch-alist' does include leading hyphens.
Also mention that 'command-switch-alist' parsing ignores equals signs
in options.

* test/lisp/startup-tests.el
(startup-tests/command-switch-alist): New unit test.

1 files changed, 9 insertions, 1 deletions

diff --git a/doc/lispref/os.texi b/doc/lispref/os.texi
index 92684c8993e..97b8b532fea 100644
--- a/doc/lispref/os.texi
+++ b/doc/lispref/os.texi
@@ -613,7 +613,7 @@ The elements of the @code{command-switch-alist} look like this:
 @end example
 
 The @sc{car}, @var{option}, is a string, the name of a command-line
-option (not including the initial hyphen).  The @var{handler-function}
+option (including the initial hyphen).  The @var{handler-function}
 is called to handle @var{option}, and receives the option name as its
 sole argument.
 
@@ -623,6 +623,14 @@ remaining command-line arguments in the variable
 @code{command-line-args-left} (see below).  (The entire list of
 command-line arguments is in @code{command-line-args}.)
 
+Note that the handling of @code{command-switch-alist} doesn't treat
+equals signs in @var{option} specially.  That is, if there's an option
+like @code{--name=value} on the command line, then only a
+@code{command-switch-alist} member whose @code{car} is literally
+@code{--name=value} will match this option.  If you want to parse such
+options, you need to use @code{command-line-functions} instead (see
+below).
+
 The command-line arguments are parsed by the @code{command-line-1}
 function in the @file{startup.el} file.  See also @ref{Emacs
 Invocation, , Command Line Arguments for Emacs Invocation, emacs, The