Add completion widget

Examples-(fish).md

@@ -41,6 +41,38 @@ function fzf-select -d 'fzf commandline job and print unescaped selection back t
 end
 ```
 
+### Completion
+
+The following can replace fish completion menu with fzf. Because of a [fish bug](https://github.com/fish-shell/fish-shell/issues/3469) this will fail on variables and other elements that need escaping (or not).
+
+```
+function fzf-complete -d 'fzf completion and print selection back to commandline'
+	set -l complist (complete -C(commandline -c))
+	set -l result
+	string join -- \n $complist | sort | eval (__fzfcmd) -m --tiebreak=index --select-1 --exit-0 --header '(commandline)' | cut -f1 | while read -l r; set result $result $r; end
+
+	for i in (seq (count $result))
+		set -l r $result[$i]
+		## We need to escape the result.
+		switch (string sub -s 1 -l 1 -- (commandline -t))
+			case "'"
+				commandline -t -- (string escape -- (eval "printf '%s' '$r'"))
+			case '"'
+				set -l quoted (string escape -- (eval "printf '%s' '$r'"))
+				set -l len (string length $quoted)
+				commandline -t -- '"'(string sub -s 2 -l (math $len - 2) (string escape -- (eval "printf '%s' '$r'")))'"'
+			case '~'
+				commandline -t -- (string sub -s 2 (string escape -n -- (eval "printf '%s' '$r'")))
+			case '*'
+				commandline -t -- (string escape -n -- (eval "printf '%s' '$r'"))
+		end
+		[ $i -lt (count $result) ]; and commandline -i ' '
+	end
+
+	commandline -f repaint
+end
+```
+
 ### Git
 
 ```