Added lines and percentage statusbar directives (#2055)

- "lines" for the number of lines in the buffer
- "percentage" for the percentage of the file at the current line

Fixes zyedidia#2049

internal/display/statusline.go

@@ -47,6 +47,12 @@ var statusInfo = map[string]func(*buffer.Buffer) string{
 		}
 		return ""
 	},
+	"lines": func(b *buffer.Buffer) string {
+		return strconv.Itoa(b.LinesNum())
+	},
+	"percentage": func(b *buffer.Buffer) string {
+		return strconv.Itoa((b.GetActiveCursor().Y + 1) * 100 / b.LinesNum())
+	},
 }
 
 func SetStatusInfoFnLua(fn string) {

runtime/help/options.md

@@ -333,7 +333,7 @@ Here are the available options:
 
 * `statusformatl`: format string definition for the left-justified part of the
    statusline. Special directives should be placed inside `$()`. Special
-   directives include: `filename`, `modified`, `line`, `col`, `opt`, `bind`.
+   directives include: `filename`, `modified`, `line`, `col`, `lines`, `percentage`, `opt`, `bind`.
    The `opt` and `bind` directives take either an option or an action afterward
    and fill in the value of the option or the key bound to the action.