Doc string clarification for keep-lines

* lisp/replace.el (keep-lines): Note that REND isn't optional if
RSTART is given (bug#44021).

diff --git a/lisp/replace.el b/lisp/replace.el
index d34cabfe89e2d876a9c3f55a8c01d71a4b5a6050..3a2ab1d24c81e4f36b1ae9d7f6125775acad1539 100644 (file)
--- a/lisp/replace.el
+++ b/lisp/replace.el
@@ -906,7 +906,8 @@ and `search-upper-case' is non-nil, the matching is case-sensitive.
 Second and third arg RSTART and REND specify the region to operate on.
 This command operates on (the accessible part of) all lines whose
 accessible part is entirely contained in the region determined by RSTART
-and REND.  (A newline ending a line counts as part of that line.)
+and REND.  (A newline ending a line counts as part of that line.)  If RSTART
+is non-nil, REND also has to be given.
 
 Interactively, in Transient Mark mode when the mark is active, operate
 on all lines whose accessible part is entirely contained in the region.