emacs-27 45a64c9 2/2: Clarify semantics of trace-function CONTEXT argument

[Noam Postavsky]

branch: emacs-27
commit 45a64c97c74c34d3d2e912a670b30aa10dbf439c
Author: Noam Postavsky <address@hidden>
Commit: Noam Postavsky <address@hidden>

    Clarify semantics of trace-function CONTEXT argument
    
    * lisp/emacs-lisp/trace.el (trace-function-foreground): Explain that
    CONTEXT should be a function, when called from Lisp.
---
 lisp/emacs-lisp/trace.el | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lisp/emacs-lisp/trace.el b/lisp/emacs-lisp/trace.el
index 5c35036..4ebb7ff 100644
--- a/lisp/emacs-lisp/trace.el
+++ b/lisp/emacs-lisp/trace.el
@@ -292,7 +292,9 @@ If `current-prefix-arg' is non-nil, also read a buffer and 
a \"context\"
 (defun trace-function-foreground (function &optional buffer context)
   "Trace calls to function FUNCTION.
 With a prefix argument, also prompt for the trace buffer (default
-`trace-buffer'), and a Lisp expression CONTEXT.
+`trace-buffer'), and a Lisp expression CONTEXT.  When called from
+Lisp, CONTEXT should be a function of no arguments which returns
+a value to insert into BUFFER during the trace.
 
 Tracing a function causes every call to that function to insert
 into BUFFER Lisp-style trace messages that display the function's