[PATCH] Document DAP 'launch' parameter

[Tom Tromey <tromey@adacore.com>]

The Debugger Adapter Protocol defines a "launch" request but leaves
the parameters up to the implementation:

    Since launching is debugger/runtime specific, the arguments for
    this request are not part of this specification.

This patch adds some documentation for the parameter GDB currently
defines.  Note that I plan to add more parameters here, and perhaps
there will be other extensions in time as well.
---
 gdb/doc/gdb.texinfo | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 940315b2713..7d5bea5dc6f 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -159,6 +159,7 @@ software in general.  We will miss him.
 * Emacs::                       Using @value{GDBN} under @sc{gnu} Emacs
 * GDB/MI::                      @value{GDBN}'s Machine Interface.
 * Annotations::                 @value{GDBN}'s annotation interface.
+* Debugger Adapter Protocol::	The Debugger Adapter Protocol.
 * JIT Interface::               Using the JIT debugging interface.
 * In-Process Agent::            In-Process Agent
 
@@ -29615,6 +29616,8 @@ the Debugger Adapter Protocol.  This protocol can be used by a
 debugger GUI or an IDE to communicate with @value{GDBN}.  This
 protocol is documented at
 @url{https://microsoft.github.io/debug-adapter-protocol/}.
+@xref{Debugger Adapter Protocol}, for information about @value{GDBN}
+extensions to the protocol.
 
 @item mi
 @cindex mi interpreter
@@ -38969,6 +38972,22 @@ source which is being displayed.  The @var{addr} is in the form @samp{0x}
 followed by one or more lowercase hex digits (note that this does not
 depend on the language).
 
+@node Debugger Adapter Protocol
+@chapter Debugger Adapter Protocol
+
+Generally, @value{GDBN} implements the Debugger Adapter Protocol as
+written.  However, in some cases, extensions are either needed or even
+expected.
+
+@value{GDBN} defines a parameter that can be passed to the
+@code{launch} request:
+
+@table @code
+@item program
+If provided, this is a string that specifies the program to use.  This
+corresponds to the @code{file} command.
+@end table
+
 @node JIT Interface
 @chapter JIT Compilation Interface
 @cindex just-in-time compilation
-- 
2.39.1