Use grep's --null option (Bug#6843)

* lisp/progmodes/grep.el (grep-use-null-filename-separator): New option.
(grep--regexp-alist-column, grep--regexp-alist-bin-matcher)
(grep-with-null-regexp-alist, grep-fallback-regexp-alist): New
constants, replacing `grep-regexp-alist'.
(grep-regex-alist): Mark the variable obsolete, add a new function of
the same name to replace it.
(grep-compute-defaults): Compute default for
`grep-use-null-filename-separator'.
(grep-mode): Set compilation-error-regexp-alist (buffer locally) to the
value of `grep-with-null-regexp-alist' or `grep-fallback-regexp-alist'
according to `grep-use-null-filename-separator'.
* lisp/progmodes/xref.el (xref-collect-matches): Call
`grep-regex-alist' instead of the obsolete variable.  Don't hardcode
grep-regexp-alist match groups.
* etc/NEWS: Announce new use of --null.  Move 'grep-save-buffers'
item under "Grep" heading as well.

1 files changed, 12 insertions, 4 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 0c2db0c398b..954fe0d547e 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -705,6 +705,18 @@ this is controlled by the 'wdired-create-parent-directories' variable.
 *** 'W' is now bound to 'browse-url-of-dired-file', and is useful for
 viewing HTML files and the like.
 
+** Grep
+
+---
+*** Grep commands will now use GNU grep's '--null' option if
+available, which allows distinguishing the filename from contents if
+they contain colons.  This can be controlled by the new custom option
+'grep-use-null-filename-separator'.
+
+*** The grep/rgrep/lgrep functions will now ask about saving files
+before running.  This is controlled by the 'grep-save-buffers'
+variable.
+
 ** Edebug
 
 *** Edebug can be prevented from pausing 1 second after reaching a
@@ -1053,10 +1065,6 @@ things like forward-word in readline work.
 ** hideshow mode got four key bindings that are analogous to outline
 mode bindings: 'C-c @ C-a', 'C-c @ C-t', 'C-c @ C-d', and 'C-c @ C-e.'
 
-** The grep/rgrep/lgrep functions will now ask about saving files
-before running.  This is controlled by the 'grep-save-buffers'
-variable.
-
 ---
 ** Customizable variable 'query-replace-from-to-separator'
 now doesn't propertize the string value of the separator.