✨ initial completion support

Closes #3

cmd/completion.go

@@ -0,0 +1,92 @@
+/*
+Copyright © 2020 James Walker <walkah@walkah.net>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+*/
+package cmd
+
+import (
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+// completionCmd represents the completion command
+var completionCmd = &cobra.Command{
+	Use:   "completion [bash|zsh|fish|powershell]",
+	Short: "Generate completion script",
+	Long: `To load completions:
+
+Bash:
+
+$ source <(workon completion bash)
+
+# To load completions for each session, execute once:
+Linux:
+  $ workon completion bash > /etc/bash_completion.d/workon
+MacOS:
+  $ workon completion bash > /usr/local/etc/bash_completion.d/workon
+
+Zsh:
+
+# If shell completion is not already enabled in your environment you will need
+# to enable it.  You can execute the following once:
+
+$ echo "autoload -U compinit; compinit" >> ~/.zshrc
+
+# To load completions for each session, execute once:
+$ workon completion zsh > "${fpath[1]}/_workon"
+
+# You will need to start a new shell for this setup to take effect.
+
+Fish:
+
+$ workon completion fish | source
+
+# To load completions for each session, execute once:
+$ workon completion fish > ~/.config/fish/completions/workon.fish
+
+Powershell:
+
+PS> workon completion powershell | Out-String | Invoke-Expression
+
+# To load completions for every new session, run:
+PS> workon completion powershell > workon.ps1
+# and source this file from your powershell profile.
+`,
+	DisableFlagsInUseLine: true,
+	ValidArgs:             []string{"bash", "zsh", "fish", "powershell"},
+	Args:                  cobra.ExactValidArgs(1),
+	Run: func(cmd *cobra.Command, args []string) {
+		switch args[0] {
+		case "bash":
+			cmd.Root().GenBashCompletion(os.Stdout)
+		case "zsh":
+			cmd.Root().GenZshCompletion(os.Stdout)
+		case "fish":
+			cmd.Root().GenFishCompletion(os.Stdout, true)
+		case "powershell":
+			cmd.Root().GenPowerShellCompletion(os.Stdout)
+		}
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(completionCmd)
+}