Improve support for the Comments field

By default hide entries in the comment field that starts with #, and
add a "comments" command to show all comments.

internal/driver/commands.go

 // pprofCommands are the report generation commands recognized by pprof.
 var pprofCommands = commands{
 	// Commands that require no post-processing.
-	"tags":     {report.Tags, nil, false, "Outputs all tags in the profile", "tags [tag_regex]* [-ignore_regex]* [>file]\nList tags with key:value matching tag_regex and exclude ignore_regex."},
-	"raw":      {report.Raw, nil, false, "Outputs a text representation of the raw profile", ""},
-	"dot":      {report.Dot, nil, false, "Outputs a graph in DOT format", reportHelp("dot", false, true)},
-	"top":      {report.Text, nil, false, "Outputs top entries in text form", reportHelp("top", true, true)},
-	"tree":     {report.Tree, nil, false, "Outputs a text rendering of call graph", reportHelp("tree", true, true)},
-	"text":     {report.Text, nil, false, "Outputs top entries in text form", reportHelp("text", true, true)},
-	"traces":   {report.Traces, nil, false, "Outputs all profile samples in text form", ""},
-	"topproto": {report.TopProto, awayFromTTY("pb.gz"), false, "Outputs top entries in compressed protobuf format", ""},
+	"comments": {report.Comments, nil, false, "Output all profile comments", ""},
 	"disasm":   {report.Dis, nil, true, "Output assembly listings annotated with samples", listHelp("disasm", true)},
+	"dot":      {report.Dot, nil, false, "Outputs a graph in DOT format", reportHelp("dot", false, true)},
 	"list":     {report.List, nil, true, "Output annotated source for functions matching regexp", listHelp("list", false)},
 	"peek":     {report.Tree, nil, true, "Output callers/callees of functions matching regexp", "peek func_regex\nDisplay callers and callees of functions matching func_regex."},
+	"raw":      {report.Raw, nil, false, "Outputs a text representation of the raw profile", ""},
+	"tags":     {report.Tags, nil, false, "Outputs all tags in the profile", "tags [tag_regex]* [-ignore_regex]* [>file]\nList tags with key:value matching tag_regex and exclude ignore_regex."},
+	"text":     {report.Text, nil, false, "Outputs top entries in text form", reportHelp("text", true, true)},
+	"top":      {report.Text, nil, false, "Outputs top entries in text form", reportHelp("top", true, true)},
+	"topproto": {report.TopProto, awayFromTTY("pb.gz"), false, "Outputs top entries in compressed protobuf format", ""},
+	"traces":   {report.Traces, nil, false, "Outputs all profile samples in text form", ""},
+	"tree":     {report.Tree, nil, false, "Outputs a text rendering of call graph", reportHelp("tree", true, true)},
 
 	// Save binary formats to a file
 	"callgrind": {report.Callgrind, awayFromTTY("callgraph.out"), false, "Outputs a graph in callgrind format", reportHelp("callgrind", false, true)},

internal/driver/driver_test.go

 		{"dot,lines,flat,focus=[12]00", "heap"},
 		{"dot,addresses,flat,ignore=[X3]002,focus=[X1]000", "contention"},
 		{"dot,files,cum", "contention"},
+		{"comments", "cpu"},
+		{"comments", "heap"},
 		{"tags", "cpu"},
 		{"tags,tagignore=tag[13],tagfocus=key[12]", "cpu"},
 		{"tags", "heap"},
 	name = addString(name, f, []string{"inuse_space", "inuse_objects", "alloc_space", "alloc_objects"})
 	name = addString(name, f, []string{"relative_percentages"})
 	name = addString(name, f, []string{"seconds"})
-	name = addString(name, f, []string{"text", "tree", "callgrind", "dot", "svg", "tags", "dot", "traces", "disasm", "peek", "weblist", "topproto"})
+	name = addString(name, f, []string{"text", "tree", "callgrind", "dot", "svg", "tags", "dot", "traces", "disasm", "peek", "weblist", "topproto", "comments"})
 	if f.strings["focus"] != "" || f.strings["tagfocus"] != "" {
 		name = append(name, "focus")
 	}
 	}
 
 	return &profile.Profile{
+		Comments:   []string{"comment", "#hidden comment"},
 		PeriodType: &profile.ValueType{Type: "allocations", Unit: "bytes"},
 		Period:     524288,
 		SampleType: []*profile.ValueType{

internal/driver/testdata/pprof.heap.comments

+comment
+#hidden comment

internal/driver/testdata/pprof.heap.flat.inuse_space.dot.focus

 digraph "unnamed" {
 node [style=filled fillcolor="#f8f8f8"]
-subgraph cluster_L { "Build ID: buildid" [shape=box fontsize=16 label="Build ID: buildid\lType: inuse_space\lShowing nodes accounting for 62.50MB, 63.37% of 98.63MB total\l"] }
+subgraph cluster_L { "Build ID: buildid" [shape=box fontsize=16 label="Build ID: buildid\lcomment\lType: inuse_space\lShowing nodes accounting for 62.50MB, 63.37% of 98.63MB total\l"] }
 N1 [label="line2001\nfile2000.src\n62.50MB (63.37%)" fontsize=24 shape=box tooltip="line2001 testdata/file2000.src (62.50MB)" color="#b21600" fillcolor="#edd8d5"]
 NN1_0 [label = "1.56MB" fontsize=8 shape=box3d tooltip="62.50MB"]
 N1 -> NN1_0 [label=" 62.50MB" weight=100 tooltip="62.50MB" labeltooltip="62.50MB"]

internal/driver/testdata/pprof.heap.flat.inuse_space.dot.focus.ignore

 digraph "unnamed" {
 node [style=filled fillcolor="#f8f8f8"]
-subgraph cluster_L { "Build ID: buildid" [shape=box fontsize=16 label="Build ID: buildid\lType: inuse_space\lShowing nodes accounting for 36.13MB, 36.63% of 98.63MB total\lDropped 2 nodes (cum <= 4.93MB)\l"] }
+subgraph cluster_L { "Build ID: buildid" [shape=box fontsize=16 label="Build ID: buildid\lcomment\lType: inuse_space\lShowing nodes accounting for 36.13MB, 36.63% of 98.63MB total\lDropped 2 nodes (cum <= 4.93MB)\l"] }
 N1 [label="line3002\nfile3000.src\n31.25MB (31.68%)\nof 32.23MB (32.67%)" fontsize=24 shape=box tooltip="line3002 testdata/file3000.src (32.23MB)" color="#b23200" fillcolor="#eddcd5"]
 NN1_0 [label = "400kB" fontsize=8 shape=box3d tooltip="31.25MB"]
 N1 -> NN1_0 [label=" 31.25MB" weight=100 tooltip="31.25MB" labeltooltip="31.25MB"]

internal/driver/testdata/pprof.heap.flat.lines.dot.focus

 digraph "unnamed" {
 node [style=filled fillcolor="#f8f8f8"]
-subgraph cluster_L { "Build ID: buildid" [shape=box fontsize=16 label="Build ID: buildid\lType: inuse_space\lShowing nodes accounting for 67.38MB, 68.32% of 98.63MB total\l"] }
+subgraph cluster_L { "Build ID: buildid" [shape=box fontsize=16 label="Build ID: buildid\lcomment\lType: inuse_space\lShowing nodes accounting for 67.38MB, 68.32% of 98.63MB total\l"] }
 N1 [label="line3000\nfile3000.src:4\n0 of 67.38MB (68.32%)" fontsize=8 shape=box tooltip="line3000 testdata/file3000.src:4 (67.38MB)" color="#b21300" fillcolor="#edd7d5"]
 N2 [label="line2001\nfile2000.src:2\n62.50MB (63.37%)\nof 63.48MB (64.36%)" fontsize=24 shape=box tooltip="line2001 testdata/file2000.src:2 (63.48MB)" color="#b21600" fillcolor="#edd8d5"]
 NN2_0 [label = "1.56MB" fontsize=8 shape=box3d tooltip="62.50MB"]

internal/driver/testdata/pprof.heap_alloc.flat.alloc_space.dot.focus

 digraph "unnamed" {
 node [style=filled fillcolor="#f8f8f8"]
-subgraph cluster_L { "Build ID: buildid" [shape=box fontsize=16 label="Build ID: buildid\lType: alloc_space\lShowing nodes accounting for 93.75MB, 95.05% of 98.63MB total\lDropped 1 node (cum <= 4.93MB)\l"] }
+subgraph cluster_L { "Build ID: buildid" [shape=box fontsize=16 label="Build ID: buildid\lcomment\lType: alloc_space\lShowing nodes accounting for 93.75MB, 95.05% of 98.63MB total\lDropped 1 node (cum <= 4.93MB)\l"] }
 N1 [label="line3002\nfile3000.src\n31.25MB (31.68%)\nof 94.73MB (96.04%)" fontsize=20 shape=box tooltip="line3002 testdata/file3000.src (94.73MB)" color="#b20200" fillcolor="#edd5d5"]
 NN1_0 [label = "400kB" fontsize=8 shape=box3d tooltip="31.25MB"]
 N1 -> NN1_0 [label=" 31.25MB" weight=100 tooltip="31.25MB" labeltooltip="31.25MB"]

internal/driver/testdata/pprof.heap_alloc.flat.alloc_space.dot.hide

 digraph "unnamed" {
 node [style=filled fillcolor="#f8f8f8"]
-subgraph cluster_L { "Build ID: buildid" [shape=box fontsize=16 label="Build ID: buildid\lType: alloc_space\lShowing nodes accounting for 93.75MB, 95.05% of 98.63MB total\lDropped 1 node (cum <= 4.93MB)\l"] }
+subgraph cluster_L { "Build ID: buildid" [shape=box fontsize=16 label="Build ID: buildid\lcomment\lType: alloc_space\lShowing nodes accounting for 93.75MB, 95.05% of 98.63MB total\lDropped 1 node (cum <= 4.93MB)\l"] }
 N1 [label="line3000\nfile3000.src\n62.50MB (63.37%)\nof 98.63MB (100%)" fontsize=24 shape=box tooltip="line3000 testdata/file3000.src (98.63MB)" color="#b20000" fillcolor="#edd5d5"]
 NN1_0 [label = "1.56MB" fontsize=8 shape=box3d tooltip="62.50MB"]
 N1 -> NN1_0 [label=" 62.50MB" weight=100 tooltip="62.50MB" labeltooltip="62.50MB"]

internal/report/report.go

 	"github.com/google/pprof/profile"
 )
 
+// Output formats.
+const (
+	Callgrind = iota
+	Comments
+	Dis
+	Dot
+	List
+	Proto
+	Raw
+	Tags
+	Text
+	TopProto
+	Traces
+	Tree
+	WebList
+)
+
+// Options are the formatting and filtering options used to generate a
+// profile.
+type Options struct {
+	OutputFormat int
+
+	CumSort             bool
+	CallTree            bool
+	DropNegative        bool
+	PositivePercentages bool
+	CompactLabels       bool
+	Ratio               float64
+	Title               string
+	ProfileLabels       []string
+
+	NodeCount    int
+	NodeFraction float64
+	EdgeFraction float64
+
+	SampleValue       func(s []int64) int64
+	SampleMeanDivisor func(s []int64) int64
+	SampleType        string
+	SampleUnit        string // Unit for the sample data from the profile.
+
+	OutputUnit string // Units for data formatting in report.
+
+	Symbol     *regexp.Regexp // Symbols to include on disassembly report.
+	SourcePath string         // Search path for source files.
+}
+
 // Generate generates a report as directed by the Report.
 func Generate(w io.Writer, rpt *Report, obj plugin.ObjTool) error {
 	o := rpt.options
 
 	switch o.OutputFormat {
+	case Comments:
+		return printComments(w, rpt)
 	case Dot:
 		return printDOT(w, rpt)
 	case Tree:
 	return nil
 }
 
+// printComments prints all freeform comments in the profile.
+func printComments(w io.Writer, rpt *Report) error {
+	p := rpt.prof
+
+	for _, c := range p.Comments {
+		fmt.Fprintln(w, c)
+	}
+	return nil
+}
+
 // printText prints a flat text report for a profile.
 func printText(w io.Writer, rpt *Report) error {
 	g, origCount, droppedNodes, _ := rpt.newTrimmedGraph()
 			label = append(label, "Build ID: "+prof.Mapping[0].BuildID)
 		}
 	}
-	label = append(label, prof.Comments...)
+	// Only include comments that do not start with '#'.
+	for _, c := range prof.Comments {
+		if !strings.HasPrefix(c, "#") {
+			label = append(label, c)
+		}
+	}
 	if o.SampleType != "" {
 		label = append(label, "Type: "+o.SampleType)
 	}
 	return fmt.Sprintf("Dropped %d %s (%s <= %s)", d, n, l, f)
 }
 
-// Output formats.
-const (
-	Proto = iota
-	Dot
-	Tags
-	Tree
-	Text
-	Traces
-	Raw
-	Dis
-	List
-	WebList
-	Callgrind
-	TopProto
-)
-
-// Options are the formatting and filtering options used to generate a
-// profile.
-type Options struct {
-	OutputFormat int
-
-	CumSort             bool
-	CallTree            bool
-	DropNegative        bool
-	PositivePercentages bool
-	CompactLabels       bool
-	Ratio               float64
-	Title               string
-	ProfileLabels       []string
-
-	NodeCount    int
-	NodeFraction float64
-	EdgeFraction float64
-
-	SampleValue       func(s []int64) int64
-	SampleMeanDivisor func(s []int64) int64
-	SampleType        string
-	SampleUnit        string // Unit for the sample data from the profile.
-
-	OutputUnit string // Units for data formatting in report.
-
-	Symbol     *regexp.Regexp // Symbols to include on disassembly report.
-	SourcePath string         // Search path for source files.
-}
-
 // New builds a new report indexing the sample values interpreting the
 // samples with the provided function.
 func New(prof *profile.Profile, o *Options) *Report {

profile/profile.go

 // String dumps a text representation of a profile. Intended mainly
 // for debugging purposes.
 func (p *Profile) String() string {
-	ss := make([]string, 0, len(p.Sample)+len(p.Mapping)+len(p.Location))
+	ss := make([]string, 0, len(p.Comments)+len(p.Sample)+len(p.Mapping)+len(p.Location))
+	for _, c := range p.Comments {
+		ss = append(ss, "Comment: "+c)
+	}
 	if pt := p.PeriodType; pt != nil {
 		ss = append(ss, fmt.Sprintf("PeriodType: %s %s", pt.Type, pt.Unit))
 	}
 				ls = append(ls, fmt.Sprintf("%s:%v", k, v))
 			}
 			sort.Strings(ls)
-			ss = append(ss, labelHeader + strings.Join(ls, " "))
+			ss = append(ss, labelHeader+strings.Join(ls, " "))
 		}
 		if len(s.NumLabel) > 0 {
 			ls := []string{}
 			for k, v := range s.NumLabel {
-				ls = append(ls,fmt.Sprintf("%s:%v", k, v))
+				ls = append(ls, fmt.Sprintf("%s:%v", k, v))
 			}
 			sort.Strings(ls)
-			ss = append(ss, labelHeader + strings.Join(ls, " "))
+			ss = append(ss, labelHeader+strings.Join(ls, " "))
 		}
 	}