Clarify doc string of 'save-buffer'

* lisp/files.el (save-buffer): Clarify that backups might not be
made even if this command is invoked with 2 or 3 "C-u"s.
(Bug#3702)

diff --git a/lisp/files.el b/lisp/files.el
index 1f97fa5f52fba3a67c5c654c620f87e6282362f3..fa630731b8d34736e454db0dac6ca40b3ad0e4f3 100644 (file)
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -4637,14 +4637,20 @@ By default, makes the previous version into a backup file
 Prefixed with one \\[universal-argument], marks this version
  to become a backup when the next save is done.
 Prefixed with two \\[universal-argument]'s,
- unconditionally makes the previous version into a backup file.
+ makes the previous version into a backup file.
 Prefixed with three \\[universal-argument]'s, marks this version
  to become a backup when the next save is done,
- and unconditionally makes the previous version into a backup file.
+ and makes the previous version into a backup file.
 
 With a numeric prefix argument of 0, never make the previous version
 into a backup file.
 
+Note that the various variables that control backups, such
+as `version-control', `backup-enable-predicate', `vc-make-backup-files',
+and `backup-inhibited', to name just the more popular ones, still
+control whether a backup will actually be produced, even when you
+invoke this command prefixed with two or three \\[universal-argument]'s.
+
 If a file's name is FOO, the names of its numbered backup versions are
  FOO.~i~ for various integers i.  A non-numbered backup file is called FOO~.
 Numeric backups (rather than FOO~) will be made if value of