Add --border-label and --border-label-pos

Close #3022

man/man1/fzf.1

@@ -226,6 +226,45 @@ Draw border around the finder
 .BR none
 .br
 
+.TP
+.BI "--border-label" [=LABEL]
+Label to print on the horizontal border line. Should be used with one of the
+following \fB--border\fR options.
+
+.br
+.B * rounded
+.br
+.B * sharp
+.br
+.B * horizontal
+.br
+.BR "* top" " (up)"
+.br
+.BR "* bottom" " (down)"
+.br
+
+.br
+e.g.
+  \fB# ANSI color codes are supported
+  # (with https://github.com/busyloop/lolcat)
+  label=$(curl -s http://metaphorpsum.com/sentences/1 | lolcat -f)
+
+  # Border label at the center
+  fzf --height=10 --border-label="╢ $label ╟" --border --color=label:italic:black
+
+  # Left-aligned (positive integer)
+  fzf --height=10 --border-label="╢ $label ╟" --border=top --border-label-pos=3 --color=label:italic:black
+
+  # Right-aligned (negative integer)
+  fzf --height=10 --border-label="╢ $label ╟" --border=bottom --border-label-pos=-3 --color=label:italic:black\fR
+
+.TP
+.BI "--border-label-pos" [=COL]
+Horizontal position of the border label on the border line. Specify a positive
+integer as the column position from the left. Specify a negative integer to
+right-align the label. The default value 0 (or \fBcenter\fR) will put
+the label at the center of the border line.
+
 .TP
 .B "--no-unicode"
 Use ASCII characters instead of Unicode box drawing characters to draw border
@@ -356,6 +395,7 @@ color mappings.
     \fBdisabled   \fRQuery string when search is disabled
     \fBinfo       \fRInfo line (match counters)
     \fBborder     \fRBorder around the window (\fB--border\fR and \fB--preview\fR)
+    \fBlabel      \fRBorder label (\fB--border-label\fR)
     \fBprompt     \fRPrompt
     \fBpointer    \fRPointer to the current line
     \fBmarker     \fRMulti-select marker