Make sure Set.GoFiles() is sorted.

and other cosmetic code changes.

cmd/pcg/main.go

diff --git a/cmd/pcg/main.go b/cmd/pcg/main.go
index 1ef0765..71924d1 100644
--- a/cmd/pcg/main.go
+++ b/cmd/pcg/main.go
@@ -393,7 +393,7 @@
 
 // Commands.
 
-func (a *application) cmdHelp(repo scm.ReadOnlyRepo, usage string) error {
+func (a *application) cmdHelp(usage string) error {
 	s := &struct {
 		Usage        string
 		Max          int
@@ -574,7 +574,6 @@
 
 // cmdRun runs all the enabled checks.
 func (a *application) cmdRun(repo scm.ReadOnlyRepo, modes []checks.Mode, against string, prereqReady *sync.WaitGroup) error {
-	var err error
 	var old scm.Commit
 	if against != "" {
 		if old = repo.Eval(against); old == scm.Invalid {
@@ -671,7 +670,7 @@
 		b := &bytes.Buffer{}
 		fs.SetOutput(b)
 		fs.PrintDefaults()
-		_ = a.cmdHelp(nil, b.String())
+		_ = a.cmdHelp(b.String())
 	}
 	verboseFlag := fs.Bool("v", checks.IsContinuousIntegration() || os.Getenv("VERBOSE") != "", "enables verbose logging output")
 	allFlag := fs.Bool("a", false, "runs checks as if all files had been modified")
@@ -739,7 +738,7 @@
 		b := &bytes.Buffer{}
 		fs.SetOutput(b)
 		fs.PrintDefaults()
-		return a.cmdHelp(repo, b.String())
+		return a.cmdHelp(b.String())
 
 	case "info":
 		if *allFlag != false {

scm/change.go

diff --git a/scm/change.go b/scm/change.go
index 5ff1a73..7d91de1 100644
--- a/scm/change.go
+++ b/scm/change.go
@@ -1,4 +1,4 @@
-// Copyright 2015 Marc-Antoine Ruel. All rights reserved.
+// Copyright 2016 Marc-Antoine Ruel. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
@@ -48,6 +48,8 @@
 
 // Set is a subset of files/directories/packages relative to the change and the
 // overall repository.
+//
+// Each list is guaranteed to be sorted according to sort.StringsAreStored().
 type Set interface {
 	// GoFiles returns all the source files, including tests.
 	GoFiles() []string
@@ -153,7 +155,11 @@
 
 	// Still need to sort these since "." will not be at the right place.
 	var wg sync.WaitGroup
-	wg.Add(4)
+	wg.Add(6)
+	go func() {
+		defer wg.Done()
+		sort.Strings(c.direct.files)
+	}()
 	go func() {
 		defer wg.Done()
 		sort.Strings(c.direct.packages)
@@ -164,6 +170,10 @@
 	}()
 	go func() {
 		defer wg.Done()
+		sort.Strings(c.all.files)
+	}()
+	go func() {
+		defer wg.Done()
 		sort.Strings(c.all.packages)
 	}()
 	go func() {
@@ -273,7 +283,12 @@
 				}
 			}
 		}
-		wg.Add(2)
+		wg.Add(3)
+		go func() {
+			defer wg.Done()
+			// TODO(maruel): This is not updated properly.
+			sort.Strings(c.indirect.files)
+		}()
 		go func() {
 			defer wg.Done()
 			sort.Strings(c.indirect.packages)
@@ -328,6 +343,9 @@
 	return c.ignorePatterns.Match(p)
 }
 
+// set implements Set.
+//
+// Items must be sorted.
 type set struct {
 	files        []string
 	packages     []string

scm/repo.go

diff --git a/scm/repo.go b/scm/repo.go
index bfcc474..b4aface 100644
--- a/scm/repo.go
+++ b/scm/repo.go
@@ -1,4 +1,4 @@
-// Copyright 2015 Marc-Antoine Ruel. All rights reserved.
+// Copyright 2016 Marc-Antoine Ruel. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
@@ -107,6 +107,7 @@
 	for _, ignorePattern := range *i {
 		for _, chunk := range chunks {
 			if matched, err := filepath.Match(ignorePattern, chunk); matched {
+				log.Printf("%s: ignored due to %q", p, ignorePattern)
 				return true
 			} else if err != nil {
 				log.Printf("bad pattern %q", ignorePattern)