Add footer

Options:
  --footer=STR             String to print as footer
  --footer-border[=STYLE]  Draw border around the footer section
                           [rounded|sharp|bold|block|thinblock|double|horizontal|vertical|
                            top|bottom|left|right|line|none] (default: line)
  --footer-label=LABEL     Label to print on the footer border
  --footer-label-pos=COL   Position of the footer label
                           [POSITIVE_INTEGER: columns from left|
                            NEGATIVE_INTEGER: columns from right][:bottom]
                           (default: 0 or center)

The default border type for footer is 'line', which draws a single
separator between the footer and the list. It changes its position
depending on `--layout`, so you don't have to manually switch between
'top' and 'bottom'

The 'line' style is now supported by other border types as well.
`--list-border` is the only exception.

src/tmux.go

@@ -11,10 +11,14 @@ func runTmux(args []string, opts *Options) (int, error) {
 	// Prepare arguments
 	fzf, rest := args[0], args[1:]
 	args = []string{"--bind=ctrl-z:ignore"}
-	if !opts.Tmux.border && opts.BorderShape == tui.BorderUndefined {
+	if !opts.Tmux.border && (opts.BorderShape == tui.BorderUndefined || opts.BorderShape == tui.BorderLine) {
 		// We append --border option at the end, because `--style=full:STYLE`
 		// may have changed the default border style.
-		rest = append(rest, "--border")
+		if tui.DefaultBorderShape == tui.BorderRounded {
+			rest = append(rest, "--border=rounded")
+		} else {
+			rest = append(rest, "--border=sharp")
+		}
 	}
 	if opts.Tmux.border && opts.Margin == defaultMargin() {
 		args = append(args, "--margin=0,1")