From 0dab006733ba21b6234932ee8f14bb6b378269c7 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Fri, 30 Sep 2022 15:37:03 +0530
Subject: [PATCH] Allow un-ambiguous prefixes for command names

---
 tools/cli/command.go    | 12 ++++++++++++
 tools/cli/group.go      |  9 +++++++++
 tools/cli/parse-args.go | 17 ++++++++++++-----
 3 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/tools/cli/command.go b/tools/cli/command.go
index 2a2dab134..4099a5a8e 100644
--- a/tools/cli/command.go
+++ b/tools/cli/command.go
@@ -333,6 +333,18 @@ func (self *Command) FindSubCommand(name string) *Command {
 	return nil
 }
 
+func (self *Command) FindSubCommands(prefix string) []*Command {
+	c := self.FindSubCommand(prefix)
+	if c != nil {
+		return []*Command{c}
+	}
+	ans := make([]*Command, 0, 4)
+	for _, g := range self.SubCommandGroups {
+		ans = g.FindSubCommands(prefix, ans)
+	}
+	return ans
+}
+
 func (self *Command) AddOptionGroup(title string) *OptionGroup {
 	for _, g := range self.OptionGroups {
 		if g.Title == title {
diff --git a/tools/cli/group.go b/tools/cli/group.go
index e69ec35f6..dbc3d2312 100644
--- a/tools/cli/group.go
+++ b/tools/cli/group.go
@@ -48,6 +48,15 @@ func (self *CommandGroup) FindSubCommand(name string) *Command {
 	return nil
 }
 
+func (self *CommandGroup) FindSubCommands(prefix string, matches []*Command) []*Command {
+	for _, c := range self.SubCommands {
+		if strings.HasPrefix(c.Name, prefix) {
+			matches = append(matches, c)
+		}
+	}
+	return matches
+}
+
 type OptionGroup struct {
 	Options []*Option
 	Title   string
diff --git a/tools/cli/parse-args.go b/tools/cli/parse-args.go
index c3b39f876..b67a4b7dd 100644
--- a/tools/cli/parse-args.go
+++ b/tools/cli/parse-args.go
@@ -95,13 +95,20 @@ func (self *Command) parse_args(ctx *Context, args []string) error {
 					options_allowed = false
 				}
 				if self.HasSubCommands() {
-					sc := self.FindSubCommand(arg)
-					if sc == nil {
-						if !self.SubCommandIsOptional {
+					possible_cmds := self.FindSubCommands(arg)
+					if len(possible_cmds) == 1 {
+						return possible_cmds[0].parse_args(ctx, args_to_parse)
+					}
+					if !self.SubCommandIsOptional {
+						if len(possible_cmds) == 0 {
 							return &ParseError{Message: fmt.Sprintf(":yellow:`%s` is not a known subcommand for :emph:`%s`. Use --help to get a list of valid subcommands.", arg, self.Name)}
 						}
-					} else {
-						return sc.parse_args(ctx, args_to_parse)
+						cn := make([]string, len(possible_cmds))
+						for i, x := range possible_cmds {
+							cn[i] = x.Name
+						}
+						return &ParseError{Message: fmt.Sprintf(
+							":yellow:`%s` is not a known subcommand for :emph:`%s`. Did you mean:\n\t%s", arg, self.Name, strings.Join(cn, "\n\t"))}
 					}
 				}
 				self.Args = append(self.Args, arg)