Log failed summary builds

[onechat] / tools.go

diff --git a/tools.go b/tools.go
index 7ca031c7d4566212486e1e42ee103a4aff5465a9..009e3312404c646f53a8fea4284371264b420a70 100644 (file)
--- a/tools.go
+++ b/tools.go
@@ -19,83 +19,57 @@ import (
 )
 
 const (
 )
 
 const (

-       // clipCharacters is the most characters of a tool output: its head and
-       // its tail, half each.
-       clipCharacters = 30000
+       // toolClipCharacters is the most characters of a tool output: its head
+       // and its tail, half each.
+       toolClipCharacters = 30000

 
 

-       // clipBytes is the most bytes that a tool keeps of each end of an
-       // output, enough for clipCharacters/2 characters of 4 bytes.
-       clipBytes = 4 * clipCharacters / 2
+       // toolClipBytes is the most bytes that a tool keeps of each end of an
+       // output, enough for toolClipCharacters/2 characters of 4 bytes.
+       toolClipBytes = 4 * toolClipCharacters / 2

 
 

-       // shellWaitDelay is how long a command can keep its output open after it
-       // ends or after its kill.
-       shellWaitDelay = 2 * time.Second
+       // toolShellWaitDelay is how long a command can keep its output open
+       // after it ends or after its kill.
+       toolShellWaitDelay = 2 * time.Second

 )
 
 )
 

-// chatLog is the log that the tools write their calls and results to.
-type chatLog interface {
+// ToolLog is the log that the tools write their calls and results to.
+type ToolLog interface {

        Append(kind, text string) (Message, error)
        Flush(ctx context.Context) error
 }
 
        Append(kind, text string) (Message, error)
        Flush(ctx context.Context) error
 }
 

-// chatReader gives the messages and the nodes that zoom and date read.
-type chatReader interface {
+// ToolChat gives the messages and the nodes that zoom and date read.
+type ToolChat interface {

        Len() int
        Message(id int) (Message, error)
        Node(level, index int) (Node, bool, error)
 }
 
        Len() int
        Message(id int) (Message, error)
        Node(level, index int) (Node, bool, error)
 }
 

-// toolbox runs the tool calls of one agent. Each call and each result goes to
+// Toolbox runs the tool calls of one agent. Each call and each result goes to

 // the log as it happens: the call as a tool message, the result as an echo
 // the log as it happens: the call as a tool message, the result as an echo

-// message. The call is durable before its tool runs, so the log never misses
-// an action outside the agent. Commands and files run as the user in the
-// working directory, with no sandbox.
-type toolbox struct {
-       log     chatLog
-       chat    chatReader
-       workdir string
-}
-
-// shellArguments are the arguments of shell.
-type shellArguments struct {
-       Command string `json:"command"`
-}
-
-// pathArguments are the arguments of read.
-type pathArguments struct {
-       Path string `json:"path"`
-}
-
-// writeArguments are the arguments of write.
-type writeArguments struct {
-       Path string `json:"path"`
-       Text string `json:"text"`
-}
-
-// editArguments are the arguments of edit.
-type editArguments struct {
-       Path string `json:"path"`
-       Old  string `json:"old"`
-       New  string `json:"new"`
-}
-
-// zoomArguments are the arguments of zoom.
-type zoomArguments struct {
-       ID int `json:"id"`
-       N  int `json:"n"`
-}
-
-// dateArguments are the arguments of date.
-type dateArguments struct {
-       ID int `json:"id"`
+// message. The call is durable before its tool runs, so the log never misses an
+// action outside the agent. Commands and files run as the user in the working
+// directory, with no sandbox. Zoom with a name reads the log of a subagent. The
+// toolbox of the agent has the runs of its subagents for spawn and tell, the
+// WhatsApp link for the WhatsApp tools, and the schedules for the schedule
+// tools. The toolbox of a subagent has none of them, so these are unknown tools
+// there.
+type Toolbox struct {
+       log       ToolLog
+       chat      ToolChat
+       subagents *Subagents
+       runs      *SubagentRuns
+       whatsapp  *WhatsApp
+       schedules *Schedules
+       workdir   string

 }
 
 // Call logs the call of the tool name with its JSON arguments, makes the log
 // durable, runs the tool, and logs its clipped output, which it returns. A
 // failed tool gives its error as the output. An error of Call itself is an
 // error of the log. When ctx ends before the flush, the tool does not run.
 }
 
 // Call logs the call of the tool name with its JSON arguments, makes the log
 // durable, runs the tool, and logs its clipped output, which it returns. A
 // failed tool gives its error as the output. An error of Call itself is an
 // error of the log. When ctx ends before the flush, the tool does not run.

-func (b *toolbox) Call(ctx context.Context, name, arguments string) (string, error) {
-       _, err := b.log.Append("tool", callText(name, arguments))
+func (b *Toolbox) Call(ctx context.Context, name, arguments string) (string, error) {
+       _, err := b.log.Append("tool", toolCallText(name, arguments))

        if err != nil {
                return "", err
        }
        if err != nil {
                return "", err
        }


@@ -107,7 +81,7 @@ func (b *toolbox) Call(ctx context.Context, name, arguments string) (string, err
 
        output := "not run: the turn was interrupted"
        if err == nil {
 
        output := "not run: the turn was interrupted"
        if err == nil {

-               output = clip(b.run(ctx, name, arguments))
+               output = toolClip(b.run(ctx, name, arguments))

        }
 
        _, err = b.log.Append("echo", output)
        }
 
        _, err = b.log.Append("echo", output)


@@ -119,46 +93,112 @@ func (b *toolbox) Call(ctx context.Context, name, arguments string) (string, err
 }
 
 // run runs one tool and returns its output, or its error as text.
 }
 
 // run runs one tool and returns its output, or its error as text.

-func (b *toolbox) run(ctx context.Context, name, arguments string) string {
+func (b *Toolbox) run(ctx context.Context, name, arguments string) string {

        var output string
        var err error
        switch name {
        case "zoom":
        var output string
        var err error
        switch name {
        case "zoom":

-               var args zoomArguments
-               err = decodeArguments(arguments, &args)
-               if err == nil {
+               var args ToolZoomArguments
+               err = toolDecodeArguments(arguments, &args)
+               switch {
+               case err != nil:
+               case args.Name != nil:
+                       output, err = b.zoomAgent(ctx, *args.Name)
+               default:

                        output, err = b.zoom(args.ID, args.N)
                }
        case "date":
                        output, err = b.zoom(args.ID, args.N)
                }
        case "date":

-               var args dateArguments
-               err = decodeArguments(arguments, &args)
+               var args ToolDateArguments
+               err = toolDecodeArguments(arguments, &args)

                if err == nil {
                        output, err = b.date(args.ID)
                }
        case "shell":
                if err == nil {
                        output, err = b.date(args.ID)
                }
        case "shell":

-               var args shellArguments
-               err = decodeArguments(arguments, &args)
+               var args ToolShellArguments
+               err = toolDecodeArguments(arguments, &args)

                if err == nil {
                        output = b.shell(ctx, args.Command)
                }
        case "read":
                if err == nil {
                        output = b.shell(ctx, args.Command)
                }
        case "read":

-               var args pathArguments
-               err = decodeArguments(arguments, &args)
+               var args ToolPathArguments
+               err = toolDecodeArguments(arguments, &args)

                if err == nil {
                        output, err = b.read(args.Path)
                }
        case "write":
                if err == nil {
                        output, err = b.read(args.Path)
                }
        case "write":

-               var args writeArguments
-               err = decodeArguments(arguments, &args)
+               var args ToolWriteArguments
+               err = toolDecodeArguments(arguments, &args)

                if err == nil {
                        output, err = b.write(args.Path, args.Text)
                }
        case "edit":
                if err == nil {
                        output, err = b.write(args.Path, args.Text)
                }
        case "edit":

-               var args editArguments
-               err = decodeArguments(arguments, &args)
+               var args ToolEditArguments
+               err = toolDecodeArguments(arguments, &args)

                if err == nil {
                        output, err = b.edit(args.Path, args.Old, args.New)
                }
                if err == nil {
                        output, err = b.edit(args.Path, args.Old, args.New)
                }

+       case "spawn":
+               var args ToolSpawnArguments
+               err = toolDecodeArguments(arguments, &args)
+               switch {
+               case b.runs == nil:
+                       err = fmt.Errorf("unknown tool %q", name)
+               case err == nil:
+                       output, err = b.runs.Spawn(ctx, args.Tasks, args.Effort)
+               }
+       case "tell":
+               var args ToolTellArguments
+               err = toolDecodeArguments(arguments, &args)
+               switch {
+               case b.runs == nil:
+                       err = fmt.Errorf("unknown tool %q", name)
+               case err == nil:
+                       output, err = b.runs.Tell(ctx, args.Name, args.Message)
+               }
+       case "whatsapp_find":
+               var args ToolWhatsAppFindArguments
+               err = toolDecodeArguments(arguments, &args)
+               switch {
+               case b.whatsapp == nil:
+                       err = fmt.Errorf("unknown tool %q", name)
+               case err == nil:
+                       output, err = b.whatsapp.Find(ctx, args.Name)
+               }
+       case "whatsapp_send":
+               var args ToolWhatsAppSendArguments
+               err = toolDecodeArguments(arguments, &args)
+               switch {
+               case b.whatsapp == nil:
+                       err = fmt.Errorf("unknown tool %q", name)
+               case err == nil:
+                       output, err = b.whatsapp.Send(ctx, args.ID, args.Chat, args.Text)
+               }
+       case "schedule_set":
+               var args ToolScheduleSetArguments
+               err = toolDecodeArguments(arguments, &args)
+               switch {
+               case b.schedules == nil:
+                       err = fmt.Errorf("unknown tool %q", name)
+               case err == nil:
+                       output, err = b.schedules.Set(args.Text, args.At, args.Cron)
+               }
+       case "schedule_list":
+               err = toolDecodeArguments(arguments, &struct{}{})
+               switch {
+               case b.schedules == nil:
+                       err = fmt.Errorf("unknown tool %q", name)
+               case err == nil:
+                       output = b.schedules.List()
+               }
+       case "schedule_remove":
+               var args ToolScheduleRemoveArguments
+               err = toolDecodeArguments(arguments, &args)
+               switch {
+               case b.schedules == nil:
+                       err = fmt.Errorf("unknown tool %q", name)
+               case err == nil:
+                       output, err = b.schedules.Remove(args.ID)
+               }

        default:
                err = fmt.Errorf("unknown tool %q", name)
        }
        default:
                err = fmt.Errorf("unknown tool %q", name)
        }


@@ -170,9 +210,19 @@ func (b *toolbox) run(ctx context.Context, name, arguments string) string {
        return output
 }
 
        return output
 }
 

+// zoomAgent returns the whole log of the subagent name.
+func (b *Toolbox) zoomAgent(ctx context.Context, name string) (string, error) {
+       subagent, err := b.subagents.Get(ctx, name)
+       if err != nil {
+               return "", err
+       }
+
+       return subagent.Show()
+}
+

 // zoom returns message id whole for n = 1, or else the two lines under the line
 // id+n.
 // zoom returns message id whole for n = 1, or else the two lines under the line
 // id+n.

-func (b *toolbox) zoom(id, n int) (string, error) {
+func (b *Toolbox) zoom(id, n int) (string, error) {

        if n < 1 || bits.OnesCount(uint(n)) != 1 || id < 0 || id%n != 0 {
                return "", fmt.Errorf("line %d+%d does not exist: n must be a power of 2 and id a multiple of n", id, n)
        }
        if n < 1 || bits.OnesCount(uint(n)) != 1 || id < 0 || id%n != 0 {
                return "", fmt.Errorf("line %d+%d does not exist: n must be a power of 2 and id a multiple of n", id, n)
        }


@@ -210,7 +260,7 @@ func (b *toolbox) zoom(id, n int) (string, error) {
 }
 
 // date returns the date and time of message id, with its weekday.
 }
 
 // date returns the date and time of message id, with its weekday.

-func (b *toolbox) date(id int) (string, error) {
+func (b *Toolbox) date(id int) (string, error) {

        if id < 0 || id >= b.chat.Len() {
                return "", fmt.Errorf("message %d does not exist", id)
        }
        if id < 0 || id >= b.chat.Len() {
                return "", fmt.Errorf("message %d does not exist", id)
        }


@@ -231,7 +281,7 @@ func (b *toolbox) date(id int) (string, error) {
 // shell runs command with bash in the working directory and returns its output
 // and error output. A failed command adds its exit status. When ctx ends, the
 // whole process group of the command is killed.
 // shell runs command with bash in the working directory and returns its output
 // and error output. A failed command adds its exit status. When ctx ends, the
 // whole process group of the command is killed.

-func (b *toolbox) shell(ctx context.Context, command string) string {
+func (b *Toolbox) shell(ctx context.Context, command string) string {

        cmd := exec.CommandContext(ctx, "bash", "-c", command)
        cmd.Dir = b.workdir
        cmd.SysProcAttr = &syscall.SysProcAttr{
        cmd := exec.CommandContext(ctx, "bash", "-c", command)
        cmd.Dir = b.workdir
        cmd.SysProcAttr = &syscall.SysProcAttr{


@@ -240,9 +290,9 @@ func (b *toolbox) shell(ctx context.Context, command string) string {
        cmd.Cancel = func() error {
                return syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
        }
        cmd.Cancel = func() error {
                return syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
        }

-       cmd.WaitDelay = shellWaitDelay
+       cmd.WaitDelay = toolShellWaitDelay

 
 

-       output := &headTail{}
+       output := &ToolHeadTail{}

        cmd.Stdout = output
        cmd.Stderr = output
        err := cmd.Run()
        cmd.Stdout = output
        cmd.Stderr = output
        err := cmd.Run()


@@ -264,7 +314,7 @@ func (b *toolbox) shell(ctx context.Context, command string) string {
 }
 
 // read returns the text of the file at path.
 }
 
 // read returns the text of the file at path.

-func (b *toolbox) read(path string) (text string, err error) {
+func (b *Toolbox) read(path string) (text string, err error) {

        file, err := os.Open(b.path(path))
        if err != nil {
                return "", err
        file, err := os.Open(b.path(path))
        if err != nil {
                return "", err


@@ -274,7 +324,7 @@ func (b *toolbox) read(path string) (text string, err error) {
                err = errors.Join(err, file.Close())
        }()
 
                err = errors.Join(err, file.Close())
        }()
 

-       output := &headTail{}
+       output := &ToolHeadTail{}

        _, err = io.Copy(output, file)
        if err != nil {
                return "", err
        _, err = io.Copy(output, file)
        if err != nil {
                return "", err


@@ -285,7 +335,7 @@ func (b *toolbox) read(path string) (text string, err error) {
 
 // write replaces the file at path with text, and makes its missing
 // directories.
 
 // write replaces the file at path with text, and makes its missing
 // directories.

-func (b *toolbox) write(path, text string) (string, error) {
+func (b *Toolbox) write(path, text string) (string, error) {

        path = b.path(path)
        err := os.MkdirAll(filepath.Dir(path), 0o755)
        if err != nil {
        path = b.path(path)
        err := os.MkdirAll(filepath.Dir(path), 0o755)
        if err != nil {


@@ -302,7 +352,7 @@ func (b *toolbox) write(path, text string) (string, error) {
 
 // edit replaces the one occurrence of old in the file at path with
 // replacement. It keeps the mode of the file.
 
 // edit replaces the one occurrence of old in the file at path with
 // replacement. It keeps the mode of the file.

-func (b *toolbox) edit(path, old, replacement string) (string, error) {
+func (b *Toolbox) edit(path, old, replacement string) (string, error) {

        path = b.path(path)
        data, err := os.ReadFile(path)
        if err != nil {
        path = b.path(path)
        data, err := os.ReadFile(path)
        if err != nil {


@@ -333,7 +383,7 @@ func (b *toolbox) edit(path, old, replacement string) (string, error) {
 
 // path returns path, relative to the working directory when it is not
 // absolute.
 
 // path returns path, relative to the working directory when it is not
 // absolute.

-func (b *toolbox) path(path string) string {
+func (b *Toolbox) path(path string) string {

        if filepath.IsAbs(path) {
                return path
        }
        if filepath.IsAbs(path) {
                return path
        }


@@ -341,24 +391,113 @@ func (b *toolbox) path(path string) string {
        return filepath.Join(b.workdir, path)
 }
 
        return filepath.Join(b.workdir, path)
 }
 

-// headTail keeps the first and the last clipBytes bytes written to it, and
-// counts the bytes between them that it drops.
-type headTail struct {
+// ToolZoomArguments are the arguments of zoom. A Name that is not nil names
+// the subagent whose whole log zoom gives, and then ID and N are not used.
+type ToolZoomArguments struct {
+       ID   int     `json:"id"`
+       N    int     `json:"n"`
+       Name *string `json:"name"`
+}
+
+// ToolDateArguments are the arguments of date.
+type ToolDateArguments struct {
+       ID int `json:"id"`
+}
+
+// ToolShellArguments are the arguments of shell.
+type ToolShellArguments struct {
+       Command string `json:"command"`
+}
+
+// ToolPathArguments are the arguments of read.
+type ToolPathArguments struct {
+       Path string `json:"path"`
+}
+
+// ToolWriteArguments are the arguments of write.
+type ToolWriteArguments struct {
+       Path string `json:"path"`
+       Text string `json:"text"`
+}
+
+// ToolEditArguments are the arguments of edit.
+type ToolEditArguments struct {
+       Path string `json:"path"`
+       Old  string `json:"old"`
+       New  string `json:"new"`
+}
+
+// ToolSpawnArguments are the arguments of spawn. A nil Effort is the effort of
+// the agent.
+type ToolSpawnArguments struct {
+       Tasks  []string `json:"tasks"`
+       Effort *string  `json:"effort"`
+}
+
+// ToolTellArguments are the arguments of tell.
+type ToolTellArguments struct {
+       Name    string `json:"name"`
+       Message string `json:"message"`
+}
+
+// ToolWhatsAppFindArguments are the arguments of whatsapp_find.
+type ToolWhatsAppFindArguments struct {
+       Name string `json:"name"`
+}
+
+// ToolWhatsAppSendArguments are the arguments of whatsapp_send.
+type ToolWhatsAppSendArguments struct {
+       ID   string `json:"id"`
+       Chat string `json:"chat"`
+       Text string `json:"text"`
+}
+
+// ToolScheduleSetArguments are the arguments of schedule_set. Exactly one of At
+// and Cron is not nil.
+type ToolScheduleSetArguments struct {
+       Text string  `json:"text"`
+       At   *string `json:"at"`
+       Cron *string `json:"cron"`
+}
+
+// ToolScheduleRemoveArguments are the arguments of schedule_remove.
+type ToolScheduleRemoveArguments struct {
+       ID int `json:"id"`
+}
+
+// ToolHeadTail keeps the first and the last toolClipBytes bytes written to it,
+// and counts the bytes between them that it drops.
+type ToolHeadTail struct {

        head    []byte
        tail    []byte
        dropped int
 }
 
        head    []byte
        tail    []byte
        dropped int
 }
 

+// String returns the output, clipped when it is too long. Invalid UTF-8 becomes
+// the replacement character.
+func (h *ToolHeadTail) String() string {
+       replacement := string(utf8.RuneError)
+       if h.dropped == 0 {
+               return toolClip(strings.ToValidUTF8(string(h.head)+string(h.tail), replacement))
+       }
+
+       head := toolFirstCharacters(strings.ToValidUTF8(string(h.head), replacement), toolClipCharacters/2)
+       tail := toolLastCharacters(strings.ToValidUTF8(string(h.tail), replacement), toolClipCharacters/2)
+       cut := len(h.head) + h.dropped + len(h.tail) - len(head) - len(tail)
+
+       return toolJoinClipped(head, tail, cut)
+}
+

 // Write keeps the bytes of p at the ends of the output.
 // Write keeps the bytes of p at the ends of the output.

-func (h *headTail) Write(p []byte) (int, error) {
+func (h *ToolHeadTail) Write(p []byte) (int, error) {

        n := len(p)
        n := len(p)

-       room := min(clipBytes-len(h.head), len(p))
+       room := min(toolClipBytes-len(h.head), len(p))

        h.head = append(h.head, p[:room]...)
        p = p[room:]
 
        h.tail = append(h.tail, p...)
        h.head = append(h.head, p[:room]...)
        p = p[room:]
 
        h.tail = append(h.tail, p...)

-       if len(h.tail) > clipBytes {
-               cut := len(h.tail) - clipBytes
+       if len(h.tail) > toolClipBytes {
+               cut := len(h.tail) - toolClipBytes

                h.dropped += cut
                h.tail = bytes.Clone(h.tail[cut:])
        }
                h.dropped += cut
                h.tail = bytes.Clone(h.tail[cut:])
        }


@@ -366,30 +505,29 @@ func (h *headTail) Write(p []byte) (int, error) {
        return n, nil
 }
 
        return n, nil
 }
 

-// String returns the output, clipped when it is too long. Invalid UTF-8 becomes
-// the replacement character.
-func (h *headTail) String() string {
-       replacement := string(utf8.RuneError)
-       if h.dropped == 0 {
-               return clip(strings.ToValidUTF8(string(h.head)+string(h.tail), replacement))
-       }
+// toolCallText returns the log text of a tool call: the name and the JSON
+// arguments.
+func toolCallText(name, arguments string) string {
+       return name + " " + arguments
+}

 
 

-       head := firstCharacters(strings.ToValidUTF8(string(h.head), replacement), clipCharacters/2)
-       tail := lastCharacters(strings.ToValidUTF8(string(h.tail), replacement), clipCharacters/2)
-       cut := len(h.head) + h.dropped + len(h.tail) - len(head) - len(tail)
+// toolClip returns text when it has at most toolClipCharacters characters.
+// Otherwise it returns the first and the last toolClipCharacters/2 characters,
+// with a mark of the cut between them.
+func toolClip(text string) string {
+       if utf8.RuneCountInString(text) <= toolClipCharacters {
+               return text
+       }

 
 

-       return joinClipped(head, tail, cut)
-}
+       head := toolFirstCharacters(text, toolClipCharacters/2)
+       tail := toolLastCharacters(text, toolClipCharacters/2)

 
 

-// callText returns the log text of a tool call: the name and the JSON
-// arguments.
-func callText(name, arguments string) string {
-       return name + " " + arguments
+       return toolJoinClipped(head, tail, len(text)-len(head)-len(tail))

 }
 
 }
 

-// decodeArguments decodes the JSON arguments of a call into args. An unknown
-// field is an error.
-func decodeArguments(arguments string, args any) error {
+// toolDecodeArguments decodes the JSON arguments of a call into args. An
+// unknown field is an error.
+func toolDecodeArguments(arguments string, args any) error {

        decoder := json.NewDecoder(strings.NewReader(arguments))
        decoder.DisallowUnknownFields()
        err := decoder.Decode(args)
        decoder := json.NewDecoder(strings.NewReader(arguments))
        decoder.DisallowUnknownFields()
        err := decoder.Decode(args)


@@ -400,28 +538,8 @@ func decodeArguments(arguments string, args any) error {
        return nil
 }
 
        return nil
 }
 

-// clip returns text when it has at most clipCharacters characters. Otherwise it
-// returns the first and the last clipCharacters/2 characters, with a mark of
-// the cut between them.
-func clip(text string) string {
-       if utf8.RuneCountInString(text) <= clipCharacters {
-               return text
-       }
-
-       head := firstCharacters(text, clipCharacters/2)
-       tail := lastCharacters(text, clipCharacters/2)
-
-       return joinClipped(head, tail, len(text)-len(head)-len(tail))
-}
-
-// joinClipped joins the head and the tail of a clipped output with a mark of
-// the cut bytes.
-func joinClipped(head, tail string, cut int) string {
-       return head + "\n[... " + strconv.Itoa(cut) + " bytes cut ...]\n" + tail
-}
-
-// firstCharacters returns the first count characters of text.
-func firstCharacters(text string, count int) string {
+// toolFirstCharacters returns the first count characters of text.
+func toolFirstCharacters(text string, count int) string {

        end := 0
        for range count {
                if end >= len(text) {
        end := 0
        for range count {
                if end >= len(text) {


@@ -435,8 +553,8 @@ func firstCharacters(text string, count int) string {
        return text[:end]
 }
 
        return text[:end]
 }
 

-// lastCharacters returns the last count characters of text.
-func lastCharacters(text string, count int) string {
+// toolLastCharacters returns the last count characters of text.
+func toolLastCharacters(text string, count int) string {

        start := len(text)
        for range count {
                if start <= 0 {
        start := len(text)
        for range count {
                if start <= 0 {


@@ -449,3 +567,9 @@ func lastCharacters(text string, count int) string {
 
        return text[start:]
 }
 
        return text[start:]
 }

+
+// toolJoinClipped joins the head and the tail of a clipped output with a mark
+// of the cut bytes.
+func toolJoinClipped(head, tail string, cut int) string {
+       return head + "\n[... " + strconv.Itoa(cut) + " bytes cut ...]\n" + tail
+}