build: generate and install completions

.gitignore

···
 knit
+knit.bash
+knit.fish
+knit.zsh

Makefile

···
 
 PREFIX ?= /usr/local
 BINDIR = $(PREFIX)/bin
+BASHDIR = $(PREFIX)/share/bash-completions/completions
+FISHDIR = $(PREFIX)/share/fish/vendor_completions.d
+ZSHDIR = $(PREFIX)/share/zsh/vendor_completions
 
 .PHONY: all build install clean
 
-all: build
+all: build completions
 
 build:
 	go build -o $(BINARY_NAME) ./cmd/knit
 
+completions: build
+	./$(BINARY_NAME) completion bash > knit.bash
+	./$(BINARY_NAME) completion fish > knit.fish
+	./$(BINARY_NAME) completion zsh > knit.zsh
+
 install: build
-	mkdir -p $(BINDIR)
-	cp $(BINARY_NAME) $(BINDIR)/$(BINARY_NAME)
+	install -d $(BINDIR)
+	install -m 755 $(BINARY_NAME) $(BINDIR)/$(BINARY_NAME)
+	install -d $(BASHDIR)
+	install -m 755 knit.bash $(BASHDIR)/knit
+	install -d $(FISHDIR)
+	install -m 755 knit.fish $(FISHDIR)/knit.fish
+	install -d $(ZSHDIR)
+	install -m 755 knit.zsh $(ZSHDIR)/_knit
 
 clean:
 	rm -f $(BINARY_NAME)
+	rm -f knit.bash
+	rm -f knit.fish
+	rm -f knit.zsh

cmd/knit/main.go

···
 		Use:   "knit",
 		Short: "knit is a CLI for tangled.sh",
 	}
+	root.CompletionOptions.HiddenDefaultCmd = true
 
 	root.AddCommand(auth.Command())
 	root.AddCommand(pr.Command())