Fix next_history() and previous_history():

* The meaning of "next" and "previous" is exchanged in readline(3) with
respect to editline(3); this part of the patch from Bastian Maerkisch.
* next_history() can move beyond the newest entry; issue pointed out
by Bastian Maerkisch, fix by me.

While here, make the documentation of ed-next-history, ed-prev-history,
H_NEXT, and H_PREV more precise.

OK czarkoff@.

3 files changed, 34 insertions, 8 deletions

diff --git a/lib/libedit/editline.3 b/lib/libedit/editline.3
index 96463db95a6..7bede329b09 100644
--- a/lib/libedit/editline.3
+++ b/lib/libedit/editline.3
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: editline.3,v 1.42 2016/04/20 01:11:45 schwarze Exp $
+.\"	$OpenBSD: editline.3,v 1.43 2016/05/10 11:07:53 schwarze Exp $
 .\"	$NetBSD: editline.3,v 1.88 2016/02/25 14:59:22 wiz Exp $
 .\"
 .\" Copyright (c) 1997-2003 The NetBSD Foundation, Inc.
@@ -27,7 +27,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: April 20 2016 $
+.Dd $Mdocdate: May 10 2016 $
 .Dt EDITLINE 3
 .Os
 .Sh NAME
@@ -731,8 +731,10 @@ Return the first element in the history.
 Return the last element in the history.
 .It Dv H_PREV
 Return the previous element in the history.
+It is newer than the current one.
 .It Dv H_NEXT
 Return the next element in the history.
+It is older than the current one.
 .It Dv H_CURR
 Return the current element in the history.
 .It Dv H_SET
diff --git a/lib/libedit/editline.7 b/lib/libedit/editline.7
index 0adf1d015ce..af80e03e577 100644
--- a/lib/libedit/editline.7
+++ b/lib/libedit/editline.7
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: editline.7,v 1.1 2016/04/20 01:11:45 schwarze Exp $
+.\"	$OpenBSD: editline.7,v 1.2 2016/05/10 11:07:53 schwarze Exp $
 .\"
 .\" Copyright (c) 2016 Ingo Schwarze <schwarze@openbsd.org>
 .\"
@@ -14,7 +14,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: April 20 2016 $
+.Dd $Mdocdate: May 10 2016 $
 .Dt EDITLINE 7
 .Os
 .Sh NAME
@@ -407,6 +407,7 @@ It is an error if the cursor is already at the end of the edit
 buffer.
 .It Ic ed-next-history Pq vi command: j, +, Ctrl-N; emacs: Ctrl-N
 Replace the edit buffer with the next history line.
+That line is older than the current line.
 With an argument, go forward by that number of history lines.
 It is a non-fatal error to advance by more lines than are available.
 .It Ic ed-next-line Pq not bound by default
@@ -426,6 +427,7 @@ It is an error if the cursor is already at the beginning of the
 edit buffer.
 .It Ic ed-prev-history Pq vi command: k, -, Ctrl-P; emacs: Ctrl-P
 Replace the edit buffer with the previous history line.
+That line is newer than the current line.
 With an argument, go back by that number of lines.
 It is a non-fatal error to back up by more lines than are available.
 .It Ic ed-prev-line Pq not bound by default
diff --git a/lib/libedit/readline.c b/lib/libedit/readline.c
index 3fae304361c..4eeb2208acf 100644
--- a/lib/libedit/readline.c
+++ b/lib/libedit/readline.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: readline.c,v 1.25 2016/05/10 10:49:37 schwarze Exp $	*/
+/*	$OpenBSD: readline.c,v 1.26 2016/05/10 11:07:53 schwarze Exp $	*/
 /*	$NetBSD: readline.c,v 1.91 2010/08/28 15:44:59 christos Exp $	*/
 
 /*-
@@ -149,6 +149,14 @@ char *rl_special_prefixes = NULL;
  */
 int rl_completion_append_character = ' ';
 
+/*
+ * When the history cursor is on the newest element and next_history()
+ * is called, GNU readline moves the cursor beyond the newest element.
+ * The editline library does not provide data structures to express
+ * that state, so we need a local flag.
+ */
+static int current_history_valid = 1;
+
 /* stuff below is used internally by libedit for readline emulation */
 
 static History *h = NULL;
@@ -280,6 +288,8 @@ rl_initialize(void)
 	int editmode = 1;
 	struct termios t;
 
+	current_history_valid = 1;
+
 	if (e != NULL)
 		el_end(e);
 	if (h != NULL)
@@ -1406,6 +1416,7 @@ add_history(const char *line)
 	(void)history(h, &ev, H_ENTER, line);
 	if (history(h, &ev, H_GETSIZE) == 0)
 		history_length = ev.num;
+	current_history_valid = 1;
 
 	return !(history_length > 0); /* return 0 if all is okay */
 }
@@ -1495,6 +1506,7 @@ clear_history(void)
 
 	(void)history(h, &ev, H_CLEAR);
 	history_length = 0;
+	current_history_valid = 1;
 }
 
 
@@ -1530,7 +1542,7 @@ HIST_ENTRY *
 current_history(void)
 {
 
-	return _move_history(H_CURR);
+	return current_history_valid ? _move_history(H_CURR) : NULL;
 }
 
 
@@ -1575,6 +1587,7 @@ history_set_pos(int pos)
 
 	(void)history(h, &ev, H_CURR);
 	curr_num = ev.num;
+	current_history_valid = 1;
 
 	/*
 	 * use H_DELDATA to set to nth history (without delete) by passing
@@ -1590,12 +1603,17 @@ history_set_pos(int pos)
 
 /*
  * returns previous event in history and shifts pointer accordingly
+ * Note that readline and editline define directions in opposite ways.
  */
 HIST_ENTRY *
 previous_history(void)
 {
 
-	return _move_history(H_PREV);
+	if (current_history_valid == 0) {
+		current_history_valid = 1;
+		return _move_history(H_CURR);
+	}
+	return _move_history(H_NEXT);
 }
 
 
@@ -1605,8 +1623,12 @@ previous_history(void)
 HIST_ENTRY *
 next_history(void)
 {
+	HIST_ENTRY *he;
 
-	return _move_history(H_NEXT);
+	he = _move_history(H_PREV);
+	if (he == NULL)
+		current_history_valid = 0;
+	return he;
 }