Add the option to not create lockfiles

* src/filelock.c (syms_of_filelock): New boolean create-lockfiles.
(lock_file): If create_lockfiles is 0, do nothing.

* lisp/cus-start.el (create-lockfiles): Add it.

Fixes: debbugs:11227

2 files changed, 13 insertions, 0 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 07d85cbf5c8..d4e38f5271c 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2012-05-10  Dave Abrahams  <dave@boostpro.com>
+
+        * filelock.c (syms_of_filelock): New boolean create-lockfiles.
+        (lock_file): If create_lockfiles is 0, do nothing.  (Bug#11227)
+
 2012-05-09  Michael Albinus  <michael.albinus@gmx.de>
 
         * dbusbind.c (xd_registered_buses): New internal Lisp object.
diff --git a/src/filelock.c b/src/filelock.c
index 2613eec4aca..d8914c73328 100644
--- a/src/filelock.c
+++ b/src/filelock.c
@@ -550,6 +550,10 @@ lock_file (Lisp_Object fn)
   struct gcpro gcpro1;
   USE_SAFE_ALLOCA;
 
+  /* Don't do locking if the user has opted out.  */
+  if (! create_lockfiles)
+    return;
+
   /* Don't do locking while dumping Emacs.
      Uncompressing wtmp files uses call-process, which does not work
      in an uninitialized Emacs.  */
@@ -722,6 +726,10 @@ syms_of_filelock (void)
                doc: /* The directory for writing temporary files.  */);
   Vtemporary_file_directory = Qnil;
 
+  DEFVAR_BOOL ("create-lockfiles", create_lockfiles,
+               doc: /* Non-nil means use lockfiles to avoid editing collisions.  */);
+  create_lockfiles = 1;
+
 #ifdef CLASH_DETECTION
   defsubr (&Sunlock_buffer);
   defsubr (&Slock_buffer);