Fix integration with git 2.18 shell completions

Wrap `git --list-cmds=others` command used by git built-in shell
completions to add a list of hub custom commands.

Fixes #1792

commands/args.go

@@ -208,6 +208,7 @@ func NewArgs(args []string) *Args {
 const (
 	noopFlag    = "--noop"
 	versionFlag = "--version"
+	listCmds    = "--list-cmds="
 	helpFlag    = "--help"
 	configFlag  = "-c"
 	chdirFlag   = "-C"
@@ -226,7 +227,7 @@ func slurpGlobalFlags(args *[]string, globalFlags *[]string) {
 		if slurpNextValue {
 			commandIndex = i + 1
 			slurpNextValue = false
-		} else if arg == versionFlag || arg == helpFlag || !looksLikeFlag(arg) {
+		} else if arg == versionFlag || arg == helpFlag || strings.HasPrefix(arg, listCmds) || !looksLikeFlag(arg) {
 			break
 		} else {
 			commandIndex = i + 1

commands/help.go

@@ -45,8 +45,15 @@ hub(1), git-help(1)
 `,
 }
 
+var cmdListCmds = &Command{
+	Key:          "--list-cmds",
+	Run:          runListCmds,
+	GitExtension: true,
+}
+
 func init() {
 	CmdRunner.Use(cmdHelp, "--help")
+	CmdRunner.Use(cmdListCmds)
 }
 
 func runHelp(helpCmd *Command, args *Args) {
@@ -89,6 +96,24 @@ func runHelp(helpCmd *Command, args *Args) {
 	}
 }
 
+func runListCmds(cmd *Command, args *Args) {
+	listOthers := false
+	parts := strings.SplitN(args.Command, "=", 2)
+	for _, kind := range strings.Split(parts[1], ",") {
+		if kind == "others" {
+			listOthers = true
+			break
+		}
+	}
+
+	if listOthers {
+		args.AfterFn(func() error {
+			ui.Println(strings.Join(customCommands(), "\n"))
+			return nil
+		})
+	}
+}
+
 func displayManPage(manPage string, args *Args) error {
 	manProgram, _ := utils.CommandPath("man")
 	if manProgram == "" {

commands/runner.go

@@ -84,12 +84,17 @@ func (r *Runner) Execute() ExecError {
 		forceFail = true
 	}
 
+	cmdName := args.Command
+	if strings.Contains(cmdName, "=") {
+		cmdName = strings.SplitN(cmdName, "=", 2)[0]
+	}
+
 	git.GlobalFlags = args.GlobalFlags // preserve git global flags
-	if !isBuiltInHubCommand(args.Command) {
+	if !isBuiltInHubCommand(cmdName) {
 		expandAlias(args)
 	}
 
-	cmd := r.Lookup(args.Command)
+	cmd := r.Lookup(cmdName)
 	if cmd != nil && cmd.Runnable() {
 		execErr := r.Call(cmd, args)
 		if execErr.ExitCode == 0 && forceFail {

features/git_compatibility.feature

@@ -5,3 +5,7 @@ Feature: git-hub compatibility
     When I successfully run `git config --global alias.branch "branch -a"`
     When I run `hub branch`
     Then the stdout should contain exactly "* master\n"
+
+  Scenario: List commands
+    When I successfully run `hub --list-cmds=others`
+    Then the stdout should contain "pull-request"