Make :earlier and :later accept arguments similar to vim

Currently the following arguments are accepted:

 {count} Go to older text state {count} times.
 {N}s    Go to older text state about {N} seconds before.
 {N}m    Go to older text state about {N} minutes before.
 {N}h    Go to older text state about {N} hours before.
 {N}d    Go to older text state about {N} days before

1 files changed, 30 insertions, 8 deletions

diff --git a/text.c b/text.c
index cb7e1c7..f19d5cb 100644
--- a/text.c
+++ b/text.c
@@ -647,14 +647,36 @@ static size_t history_traverse_to(Text *txt, Action *a) {
 	return pos;
 }
 
-size_t text_earlier(Text *txt) {
-	Action *earlier = txt->history->earlier;
-	return history_traverse_to(txt, earlier);
-}
-
-size_t text_later(Text *txt) {
-	Action *later = txt->history->later;
-	return history_traverse_to(txt, later);
+size_t text_earlier(Text *txt, int count) {
+	Action *a = txt->history;
+	while (count-- > 0 && a->earlier)
+		a = a->earlier;
+	return history_traverse_to(txt, a);
+}
+
+size_t text_later(Text *txt, int count) {
+	Action *a = txt->history;
+	while (count-- > 0 && a->later)
+		a = a->later;
+	return history_traverse_to(txt, a);
+}
+
+size_t text_restore(Text *txt, time_t time) {
+	Action *a = txt->history;
+	while (time < a->time && a->earlier)
+		a = a->earlier;
+	while (time > a->time && a->later)
+		a = a->later;
+	time_t diff = labs(a->time - time);
+	if (a->earlier && a->earlier != txt->history && labs(a->earlier->time - time) < diff)
+		a = a->earlier;
+	if (a->later && a->later != txt->history && labs(a->later->time - time) < diff)
+		a = a->earlier;
+	return history_traverse_to(txt, a);
+}
+
+time_t text_state(Text *txt) {
+	return txt->history->time;
 }
 
 bool text_save(Text *txt, const char *filename) {