Embed shell integration scripts in fzf binary (--bash / --zsh / --fish) (#3675)

This simplifies the distribution, and the users are less likely to have
problems caused by using incompatible scripts and binaries.

    # Set up fzf key bindings and fuzzy completion
    eval "$(fzf --bash)"

    # Set up fzf key bindings and fuzzy completion
    eval "$(fzf --zsh)"

    # Set up fzf key bindings
    fzf --fish | source

main.go

@@ -1,6 +1,10 @@
 package main
 
 import (
+	_ "embed"
+	"fmt"
+	"strings"
+
 	fzf "github.com/junegunn/fzf/src"
 	"github.com/junegunn/fzf/src/protector"
 )
@@ -8,7 +12,44 @@ import (
 var version string = "0.47"
 var revision string = "devel"
 
+//go:embed shell/key-bindings.bash
+var bashKeyBindings []byte
+
+//go:embed shell/completion.bash
+var bashCompletion []byte
+
+//go:embed shell/key-bindings.zsh
+var zshKeyBindings []byte
+
+//go:embed shell/completion.zsh
+var zshCompletion []byte
+
+//go:embed shell/key-bindings.fish
+var fishKeyBindings []byte
+
+func printScript(label string, content []byte) {
+	fmt.Println("### " + label + " ###")
+	fmt.Println(strings.TrimSpace(string(content)))
+	fmt.Println("### end: " + label + " ###")
+}
+
 func main() {
 	protector.Protect()
-	fzf.Run(fzf.ParseOptions(), version, revision)
+	options := fzf.ParseOptions()
+	if options.Bash {
+		printScript("key-bindings.bash", bashKeyBindings)
+		printScript("completion.bash", bashCompletion)
+		return
+	}
+	if options.Zsh {
+		printScript("key-bindings.zsh", zshKeyBindings)
+		printScript("completion.zsh", zshCompletion)
+		return
+	}
+	if options.Fish {
+		printScript("key-bindings.fish", fishKeyBindings)
+		fmt.Println("fzf_key_bindings")
+		return
+	}
+	fzf.Run(options, version, revision)
 }