readline: Automatically do word completion based on history

tools/cli/command.go

@@ -560,18 +560,18 @@ func (self *Command) Exec(args ...string) {
 }
 
 func (self *Command) GetCompletions(argv []string, init_completions func(*Completions)) *Completions {
-	ans := Completions{Groups: make([]*MatchGroup, 0, 4)}
+	ans := NewCompletions()
 	if init_completions != nil {
-		init_completions(&ans)
+		init_completions(ans)
 	}
 	if len(argv) > 0 {
 		exe := argv[0]
 		cmd := self.FindSubCommand(exe)
 		if cmd != nil {
 			if cmd.ParseArgsForCompletion != nil {
-				cmd.ParseArgsForCompletion(cmd, argv[1:], &ans)
+				cmd.ParseArgsForCompletion(cmd, argv[1:], ans)
 			} else {
-				completion_parse_args(cmd, argv[1:], &ans)
+				completion_parse_args(cmd, argv[1:], ans)
 			}
 		}
 	}
@@ -582,5 +582,5 @@ func (self *Command) GetCompletions(argv []string, init_completions func(*Comple
 		}
 	}
 	ans.Groups = non_empty_groups
-	return &ans
+	return ans
 }

tools/cli/completion.go

@@ -115,12 +115,46 @@ type Completions struct {
 	split_on_equals bool // true if the cmdline is split on = (BASH does this because readline does this)
 }
 
+func NewCompletions() *Completions {
+	return &Completions{Groups: make([]*MatchGroup, 0, 4)}
+}
+
 func (self *Completions) AddPrefixToAllMatches(prefix string) {
 	for _, mg := range self.Groups {
 		mg.AddPrefixToAllMatches(prefix)
 	}
 }
 
+func (self *Completions) MergeMatchGroup(mg *MatchGroup) {
+	if len(mg.Matches) == 0 {
+		return
+	}
+	var dest *MatchGroup
+	for _, q := range self.Groups {
+		if q.Title == mg.Title {
+			dest = q
+			break
+		}
+	}
+	if dest == nil {
+		dest = self.AddMatchGroup(mg.Title)
+		dest.NoTrailingSpace = mg.NoTrailingSpace
+		dest.IsFiles = mg.IsFiles
+	}
+	seen := utils.NewSet[string](64)
+	for _, q := range self.Groups {
+		for _, m := range q.Matches {
+			seen.Add(m.Word)
+		}
+	}
+	for _, m := range mg.Matches {
+		if !seen.Has(m.Word) {
+			seen.Add(m.Word)
+			dest.Matches = append(dest.Matches, m)
+		}
+	}
+}
+
 func (self *Completions) AddMatchGroup(title string) *MatchGroup {
 	for _, q := range self.Groups {
 		if q.Title == title {