bug#20333: 24.3; Add warning about shell quoting to documentation of combine-and-quote-strings

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tags 20333 patch
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Philipp Stephani <p.stephani2@gmail.com> writes:

> Context and more discussion:
> http://lists.gnu.org/archive/html/help-gnu-emacs/2015-04/msg00179.html
>
> It would be great if the documentation string and the Elisp manual about
> `combine-and-quote-strings' could be made a bit clearer by explicitly
> stating that this function is not useful for shell quoting.

How about this:

>From 5a1d23231bcf3c279fd3b09654fb132513748e6c Mon Sep 17 00:00:00 2001
From: Noam Postavsky <npostavs@gmail.com>
Date: Sun, 3 Jul 2016 09:56:36 -0400
Subject: [PATCH v1] Note combine-and-quote-strings doesn't shell quote

* doc/lispref/processes.texi (Shell Arguments):
* lisp/subr.el (combine-and-quote-strings): Add a note that
combine-and-quote-strings doesn't protect arguments against shell
evaluation (Bug #20333).
---
 doc/lispref/processes.texi | 5 +++++
 lisp/subr.el               | 5 ++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/doc/lispref/processes.texi b/doc/lispref/processes.texi
index 5bd0b11..b4542f6 100644
--- a/doc/lispref/processes.texi
+++ b/doc/lispref/processes.texi
@@ -215,6 +215,11 @@ Shell Arguments
 string arguments to be passed to @code{call-process} or
 @code{start-process}, or for converting such lists of arguments into
 a single Lisp string to be presented in the minibuffer or echo area.
+Note that if a shell is involved (e.g., if using
+@code{call-process-shell-command}), arguments should still be
+protected by @code{shell-quote-argument};
+@code{combine-and-quote-strings} is @emph{not} intended to protect
+special characters from shell evaluation.
 
 @defun split-string-and-unquote string &optional separators
 This function splits @var{string} into substrings at matches for the
diff --git a/lisp/subr.el b/lisp/subr.el
index ed2166a..e9e19d3 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -3706,7 +3706,10 @@ combine-and-quote-strings
   "Concatenate the STRINGS, adding the SEPARATOR (default \" \").
 This tries to quote the strings to avoid ambiguity such that
   (split-string-and-unquote (combine-and-quote-strings strs)) == strs
-Only some SEPARATORs will work properly."
+Only some SEPARATORs will work properly.
+
+Note that this is not intended to protect STRINGS from
+interpretation by shells, use `shell-quote-argument' for that."
   (let* ((sep (or separator " "))
          (re (concat "[\\\"]" "\\|" (regexp-quote sep))))
     (mapconcat
-- 
2.8.0