// repotool queries and manipulate multiple repository types in a uniform way.
package main

// Copyright by Eric S. Raymond
// SPDX-License-Identifier: BSD-2-Clause

import (
	"bufio"
	"bytes"
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"os"
	"os/exec"
	"path"
	"path/filepath"
	"regexp"

	"sort"
	"strconv"
	"strings"
	"text/template"
	"time"

	readline "github.com/chzyer/readline"
	difflib "github.com/ianbruene/go-difflib/difflib"
	term "golang.org/x/term"
)

var version string // Patched by -X option in Makefile

// Define a couplee of partial capability tables for querying
// checkout directories.

var cvsCheckout = VCS{
	name:         "cvs-checkout",
	subdirectory: "CVS",
	taglister:    "",
	branchlister: "",
}

var svnCheckout = VCS{
	name:         "svn-checkout",
	subdirectory: ".svn",
	taglister:    "ls tags 2>/dev/null || exit 0",
	branchlister: "ls branches 2>/dev/null || exit 0",
}

func init() {
	setInit()
	vcsInit()
	vcstypes = append(vcstypes, cvsCheckout)
	vcstypes = append(vcstypes, svnCheckout)
}

type squishyParts struct {
	Project   string
	SourceVCS string
	TargetVCS string
}

var makefileTemplate = `# Makefile for {{.Project}} conversion using reposurgeon
#
# Steps to using this:
# 1. Make sure reposurgeon and repotool are on your $PATH.
# 2. (Skip this step if you're starting from a stream file.) For svn, set
#    REMOTE_URL to point at the remote repository you want to convert;
#    you can use either an svn: URL, an rsync: URL, or a p4: URL for this.
#    If the repository is already in a DVCS such as hg or git,
#    set REMOTE_URL to either the normal cloning URL (starting with hg://,
#    git://, etc.) or to the path of a local clone.
# 3. For cvs, set CVS_HOST to the repo hostname and CVS_MODULE to the module,
#    then uncomment the line that builds REMOTE_URL 
#    Note: for CVS hosts other than Sourceforge or Savannah you will need to 
#    include the path to the CVS modules directory after the hostname.
# 4. Set any required read options, such as --user-ignores
#    by setting READ_OPTIONS.
# 5. Optionally, replace the default value of DUMPFILTER with a
#    command or pipeline that actually filters the dump rather than
#    just copying it through.  The most usual reason to do this is
#    that your Subversion repository is multiproject and you want to
#    strip out one subtree for conversion with repocutter sift and pop
#    commands.  Note that if you ever did copies across project
#    subtrees this simple stripout will not work - you are in deep
#    trouble and should find an expert to advise you
# 6. Run 'make stubmap' to create a stub author map.
# 7. Run 'make' to build a converted repository.
#
# For a production-quality conversion you will need to edit the map
# file and the lift script.  During the process you can set EXTRAS to
# name extra metadata such as a comments message-box that the final.
# conversion depends on.
#
# Afterwards, you can use the *compare productions to check your work.
#

EXTRAS = 
REMOTE_URL = svn://svn.debian.org/{{.Project}}
CVS_HOST = cvs.sourceforge.net
#CVS_HOST = cvs.savannah.gnu.org
CVS_MODULE = {{.Project}}
#REMOTE_URL = cvs://$(CVS_HOST)/{{.Project}}\#$(CVS_MODULE)
READ_OPTIONS =
#CHECKOUT_OPTIONS = --ignore-externals
DUMPFILTER = cat
VERBOSITY = "set progress"
REPOSURGEON = reposurgeon
LOGFILE = conversion.log

# Set and uncomment these if remote access to Subversion needs credentials.
#export RUSERNAME=
#export RPASSWORD=

# Configuration ends here

.PHONY: local-clobber remote-clobber gitk gc compare clean stubmap

default: {{.Project}}-{{.TargetVCS}}

# Build the repository from the stream dump
{{.Project}}-{{.TargetVCS}}: {{.Project}}.{{.SourceVCS}} {{.Project}}.opts {{.Project}}.lift {{.Project}}.map $(EXTRAS)
	$(REPOSURGEON) $(VERBOSITY) 'logfile $(LOGFILE)' 'script {{.Project}}.opts' "read $(READ_OPTIONS) <{{.Project}}.{{.SourceVCS}}" 'authors read <{{.Project}}.map' 'sourcetype {{.SourceVCS}}' 'prefer git' 'script {{.Project}}.lift' 'legacy write >{{.Project}}.fo' 'rebuild {{.Project}}-{{.TargetVCS}}'

# Build a stream dump from the local mirror
{{.Project}}.{{.SourceVCS}}: {{.Project}}-mirror
	(cd {{.Project}}-mirror/ >/dev/null; repotool export) | $(DUMPFILTER) >{{.Project}}.{{.SourceVCS}}

# Build a local mirror of the remote repository
{{.Project}}-mirror:
	repotool mirror $(REMOTE_URL) {{.Project}}-mirror

# Make a local checkout of the source mirror for inspection
%-checkout: %-mirror
	cd %-mirror >/dev/null; repotool checkout $(CHECKOUT_OPTIONS) $(PWD)/%-checkout

# Force rebuild of stream from the local mirror on the next make
local-clobber: clean
	rm -fr {{.Project}}.fi {{.Project}}-{{.TargetVCS}}

# Force full rebuild from the remote repo on the next make.
remote-clobber: local-clobber
	rm -fr {{.Project}}.{{.SourceVCS}} *-mirror *-checkout

# Get the (empty) state of the author mapping from the first-stage stream
stubmap: {{.Project}}.{{.SourceVCS}}
	$(REPOSURGEON) $(VERBOSITY) "read $(READ_OPTIONS) <{{.Project}}.{{.SourceVCS}}" 'authors write >{{.Project}}.map'

# Compare the histories of the unconverted and converted repositories at head
# and all tags.
headcompare: {{.Project}}-mirror {{.Project}}-{{.TargetVCS}}
	repotool compare {{.Project}}-mirror {{.Project}}-{{.TargetVCS}}
tagscompare: {{.Project}}-mirror {{.Project}}-{{.TargetVCS}}
	repotool compare-tags {{.Project}}-mirror {{.Project}}-{{.TargetVCS}}
branchescompare: {{.Project}}-mirror {{.Project}}-{{.TargetVCS}}
	repotool compare-branches {{.Project}}-mirror {{.Project}}-{{.TargetVCS}}
allcompare: {{.Project}}-mirror {{.Project}}-{{.TargetVCS}}
	repotool compare-all {{.Project}}-mirror {{.Project}}-{{.TargetVCS}}

# General cleanup and utility
clean:
	rm -fr *~ .rs* {{.Project}}-conversion.tar.gz *.{{.SourceVCS}} *.fi *.fo
`

var gitTemplateAdditions = `
#
# The following productions are git-specific
#

# Browse the generated git repository
gitk: {{.Project}}-git
	cd {{.Project}}-git; gitk --all

# Run a garbage-collect on the generated git repository.  Import doesn't.
# This repack call is the active part of gc --aggressive.  This call is
# tuned for very large repositories.
gc: {{.Project}}-git
	cd {{.Project}}-git; time git -c pack.threads=1 repack -AdF --window=1250 --depth=250
`

var acceptMissing bool
var context bool
var nobranch bool
var seeignores bool
var quiet bool
var same bool
var unified bool
var verbose bool
var progress bool

var branch string
var comparemode string
var refexclude string
var revision string
var basedir string
var tag string
var passthrough string

func croak(msg string, args ...interface{}) {
	content := fmt.Sprintf(msg, args...)
	os.Stderr.WriteString("repotool: " + content + "\n")
	os.Exit(1)
}

func announce(msg string, args ...interface{}) {
	if !quiet {
		content := fmt.Sprintf(msg, args...)
		os.Stdout.WriteString("repotool: " + content + "\n")
	}
}

func complain(msg string, args ...interface{}) {
	if !quiet {
		content := fmt.Sprintf(msg, args...)
		os.Stderr.WriteString("repotool: " + content + "\n")
	}
}

// Either execute a command or die noisily
func runShellProcessOrDie(dcmd string, legend string) {
	if legend != "" {
		legend = " " + legend
	}
	if verbose {
		announce("executing '%s'%s", dcmd, legend)
	}
	cmd := exec.Command("sh", "-c", "("+dcmd+")")
	cmd.Stdin = os.Stdin
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	err := cmd.Run()
	if err != nil {
		croak("executing %q: %v", dcmd, err)
	}
}

// Either execute a command with line-by-line monitoring of output or die noisily
func runMonitoredProcessOrDie(dcmd string, legend string, hook func(string)) {
	if legend != "" {
		legend = " " + legend
	}
	if verbose {
		announce("monitoring '%s'%s", dcmd, legend)
	}
	cmd := exec.Command("sh", "-c", "("+dcmd+")")
	pipeReader, pipeWriter := io.Pipe()
	cmd.Stdin = os.Stdin
	cmd.Stdout = pipeWriter
	cmd.Stderr = os.Stderr

	scanner := bufio.NewScanner(pipeReader)
	scanner.Split(bufio.ScanLines)
	go func() {
		for scanner.Scan() {
			hook(scanner.Text())
		}
	}()

	err := cmd.Run()
	if err != nil {
		croak("executing %q: %v", dcmd, err)
	}
}

// captureFromProcess runs a specified command, capturing the output.
func captureFromProcess(command string, legend string) string {
	if verbose {
		announce("%s: capturing %s%s", time.Now(), command, legend)
	}
	cmd := exec.Command("sh", "-c", command)
	content, err := cmd.CombinedOutput()
	if err != nil {
		croak("executing %q: %v", cmd, err)
	}
	if verbose {
		announce(string(content))
	}
	return string(content)
}

func under(target string, hook func()) {
	if verbose {
		fmt.Printf("repotool: in %s...\n", target)
	}
	source, err := os.Getwd()
	if err != nil {
		log.Fatal(err)
	}
	if isdir(target) {
		os.Chdir(target)
	} else {
		err = os.Chdir(filepath.Dir(target))
		if err != nil {
			log.Fatal(err)
		}
	}
	hook()
	os.Chdir(source)
}

func isDvcsOrCheckout() bool {
	// Is this a DVCS or checkout where we can compare files?
	t := identifyRepo(".")
	return t != nil && t.name != "cvs" && t.name != "svn"
}

func input(prompt string) string {
	rl, err := readline.New(prompt)
	if err != nil {
		log.Fatal(err)
	}
	defer rl.Close()
	line, _ := rl.Readline()
	return line
}

func makeStub(name string, contents string) {
	fp, err := os.OpenFile(name, os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		log.Fatal(err)
	}
	defer fp.Close()
	fp.WriteString(contents)
}

func initialize(args []string) {
	WriteSupport := newStringSet()
	for _, vcs := range vcstypes {
		if vcs.importer != "" {
			WriteSupport.Add(vcs.name)
		}
	}
	ReadSupport := newStringSet()
	for _, vcs := range vcstypes {
		if vcs.exporter != "" {
			ReadSupport.Add(vcs.name)
		}
	}
	// Hacky special case implemented through extractor class
	ReadSupport.Add("hg")
	if verbose {
		fmt.Printf("initialize args: %v\n", args)
	}
	var squishy squishyParts
	if len(args) < 1 {
		croak("initialize requires a project name.")
	}
	project, args := args[0], args[1:]
	squishy.Project = project
	if len(args) == 0 {
		squishy.SourceVCS = input("repotool: what VCS do you want to convert from? ")
	} else {
		squishy.SourceVCS, args = args[0], args[1:]
	}
	if !ReadSupport.Contains(squishy.SourceVCS) {
		croak("unknown source VCS type %s", squishy.SourceVCS)
	}
	if len(args) == 0 {
		squishy.TargetVCS = input("repotool: what VCS do you want to convert to? ")
	} else {
		squishy.TargetVCS = args[0]
		args = args[1:]
	}
	if !WriteSupport.Contains(squishy.TargetVCS) {
		croak("unknown target VCS type %s", squishy.TargetVCS)
	}
	if exists("Makefile") {
		complain("a Makefile already exists here.")
	} else {
		if !quiet {
			fmt.Printf("repotool: generating Makefile, some variables in it need to be set.\n")
		}
		instructions := makefileTemplate
		if squishy.TargetVCS == "git" {
			instructions += gitTemplateAdditions
		}
		// Create a new template and parse the letter into it.
		t := template.Must(template.New("Makefile").Parse(instructions))
		fp, err := os.OpenFile("Makefile", os.O_CREATE|os.O_WRONLY, 0644)
		if err != nil {
			log.Fatal(err)
		}
		defer fp.Close()
		err2 := t.Execute(fp, squishy)
		if err2 != nil {
			log.Println("executing template:", err2)
		}
	}
	if exists(project + ".opts") {
		complain("a project options file already exists here.")
	} else {
		if !quiet {
			fmt.Printf("repotool: generating a stub options file.\n")
		}
		makeStub(project+".opts", "# Pre-read options for reposurgeon go here.\n")
	}
	if exists(project + ".lift") {
		complain("a project lift file already exists here.")
	} else {
		if !quiet {
			fmt.Printf("repotool: generating a stub lift file.\n")
		}
		makeStub(project+".lift", fmt.Sprintf("# Lift commands for %s\n", project))
	}
	if exists(project + ".map") {
		complain("a project map file already exists here.")
	} else {
		if !quiet {
			fmt.Printf("repotool: generating a stub map file.\n")
		}
		makeStub(project+".map", fmt.Sprintf("# Author map for %s\n", project))
	}
}

func export() {
	pwd, err := os.Getwd()
	if err != nil {
		log.Fatal(err)
	}
	rt := identifyRepo(".")
	if rt == nil {
		croak("unknown repository type at %s", pwd)
	}
	cmd := rt.exporter
	if rt.name == "hg" {
		// Grotty repotool-only special case that takes the long way around
		// through reposurgeon's extractor classes.  Remove if and when there
		// is a real exporter for hg
		cmd = "reposurgeon 'read .' 'prefer git' 'write -'"
	}
	if cmd == "" {
		croak("can't export from repository of type %s.", rt.name)
	} else {
		if rt.quieter != "" {
			cmd += " " + rt.quieter
		}
		runShellProcessOrDie(cmd, " export command in "+pwd)
	}
}

func mirror(args []string) {
	if verbose {
		fmt.Printf("mirror args: %v\n", args)
	}
	operand := args[0]
	mirrordir := ""
	if len(args) >= 2 {
		mirrordir = args[1]
	}
	pwd, err := os.Getwd()
	if err != nil {
		log.Fatal(err)
	}
	// Identifies local repositories of a specified type
	localrepo := func(operand string, prefix string, vcs string) bool {
		if !strings.HasPrefix(operand, prefix) {
			return false
		}
		vtype := identifyRepo(operand[len(prefix)-1:])
		return vtype != nil && vtype.name == vcs
	}
	username := os.Getenv("RUSERNAME")
	password := os.Getenv("RPASSWORD")
	plausibleSVNPrefix := func(operand string) bool {
		return strings.HasPrefix(operand, "svn://") || strings.HasPrefix(operand, "svn+ssh://") || strings.HasPrefix(operand, "file://") || strings.HasPrefix(operand, "https://") || strings.HasPrefix(operand, "http://")
	}
	// Gets commit length of a Subversion repo from its URL. Can be run
	// on a local mirror directory.
	reposize := func(operand string) int {
		if !plausibleSVNPrefix(operand) {
			operand = "file://" + operand
		}
		infoCredentials := ""
		if username != "" {
			infoCredentials = fmt.Sprintf("--username %q", username)
		}
		if password != "" {
			infoCredentials += fmt.Sprintf(" --password %q", password)
		}
		s := captureFromProcess(fmt.Sprintf("svn info --show-item=revision %s %s", infoCredentials, operand), "info")
		revs, _ := strconv.Atoi(strings.Trim(s, "\n"))
		return revs
	}
	var locald string
	tillHash := regexp.MustCompile("^.*#")
	isFullURL, badre := regexp.Match("svn://|svn\\+ssh://|https://|http://", []byte(operand))
	if (badre == nil && isFullURL) || localrepo(operand, "file:///", "svn") {
		if mirrordir == "" {
			locald = filepath.Join(pwd, filepath.Base(operand)+"-mirror")
		} else if mirrordir[0] == os.PathSeparator {
			locald = mirrordir
		} else {
			locald = filepath.Join(pwd, mirrordir)
		}
		mirrorCredentials := ""
		if username != "" {
			mirrorCredentials = fmt.Sprintf("--source-username %q", username)
		}
		if password != "" {
			mirrorCredentials += fmt.Sprintf(" --source-password %q", password)
		}
		runShellProcessOrDie("svnadmin create "+locald, "mirror creation")
		makeStub(locald+"/hooks/pre-revprop-change", "#!/bin/sh\nexit 0;\n")
		os.Remove(locald + "/hooks/post-revprop-change")
		// Note: The --allow-non-empty and --steal-lock options permit
		// this to operate on a Subversion repository you have pulled
		// in with rsync (which is very much faster than mirroring via
		// SVN protocol), but they disable some safety checking.  Be
		// very sure you have not made any local changes to the repo
		// since rsyncing, or havoc will ensue.
		runShellProcessOrDie(fmt.Sprintf("chmod a+x %s/hooks/pre-revprop-change", locald), "mirroring")
		runShellProcessOrDie(fmt.Sprintf("svnsync init -q %s --allow-non-empty file://%s %s", mirrorCredentials, locald, operand), "mirroring")
		baton := newBaton(progress, func(s string) {})
		baton.startProgress("Mirroring", uint64(reposize(operand)))
		cmd := fmt.Sprintf("svnsync synchronize %s --steal-lock file://%s", mirrorCredentials, locald)
		ind := 0
		runMonitoredProcessOrDie(cmd, "mirroring", func(line string) {
			if strings.Contains(line, "Committed revision") {
				ind++
				baton.percentProgress(uint64(ind))
			}
		})
		baton.endProgress()
	} else if strings.HasPrefix("p4://", operand) {
		// According to
		// https://stackoverflow.com/questions/31051732/perforce-to-git-migration,
		// the clone operation will create a live Git repository capturing the
		// Perforce history.
		operand = operand[3:]
		if mirrordir == "" {
			locald = filepath.Join(pwd, filepath.Base(operand)+"-mirror")
		} else if mirrordir[0] == os.PathSeparator {
			locald = mirrordir
		} else {
			locald = filepath.Join(pwd, mirrordir)
		}
		cmd := ""
		legend := ""
		if isdir(mirrordir) {
			cmd = "git p4 sync --import-labels --detect-branches --destination %s %s@all"
			legend = "p4 syncing"
		} else {
			cmd = fmt.Sprintf("git p4 clone --import-labels --detect-branches --destination %s %s@all")
			legend = "p4 cloning"
		}
		runShellProcessOrDie(fmt.Sprintf(cmd, mirrordir, operand), legend)
	} else if isdir(filepath.Join(operand, "locks")) {
		if operand[0] == os.PathSeparator {
			locald = operand
		} else {
			locald = filepath.Join(pwd, operand)
		}
		mirrorCredentials := ""
		if username != "" {
			mirrorCredentials = fmt.Sprintf("--source-username %q", username)
		}
		if password != "" {
			mirrorCredentials += fmt.Sprintf(" --source-password %q", password)
		}
		getremote := fmt.Sprintf("svnlook pg %s -r 0 --revprop svn:sync-from-url", operand)
		cmd := fmt.Sprintf("svnsync synchronize -q --steal-lock %s file://%s", mirrorCredentials, locald)
		if remote := captureFromProcess(getremote, "getting remote URL"); !plausibleSVNPrefix(remote) {
			// Without the remote size we can't progress-meter.
			// Might happen if we rsynced this.
			runShellProcessOrDie(cmd, "mirroring")
		} else {
			// Have remote size, we can progress-meter,
			// this makes long resyncs more bearable.
			baton := newBaton(progress, func(s string) {})
			remotesize := reposize(remote)
			localsize := reposize(locald)
			baton.startProgress("Mirroring", uint64(remotesize-localsize))
			ind := 0
			runMonitoredProcessOrDie(cmd, "mirroring", func(line string) {
				if strings.Contains(line, "Committed revision") {
					ind++
					baton.percentProgress(uint64(ind))
				}
			})
			baton.endProgress()
		}
	} else if strings.HasPrefix(operand, "rsync://") {
		if mirrordir == "" {
			locald = filepath.Join(pwd, filepath.Base(operand)+"-mirror")
		} else if mirrordir[0] == os.PathSeparator {
			locald = mirrordir
		} else {
			locald = filepath.Join(pwd, mirrordir)
		}
		// Sadly, due to a limitation of rsync we can't simply copy over the rsync URL.
		// Those can't be tested locally and they tell rsync to look for rsyncd on the server
		// side. So, we're going to transform the source address to a : spec.
		parts := strings.SplitN(operand[8:], "/", 2)
		operand = parts[0] + ":/" + parts[1]
		runShellProcessOrDie(fmt.Sprintf("rsync --delete -az %s/ %s", operand, locald), "mirroring")
	} else if strings.HasPrefix(operand, "cvs://") || localrepo(operand, "file://", "cvs") {
		if mirrordir != "" {
			locald = mirrordir
		} else {
			locald = tillHash.ReplaceAllString(filepath.Base(operand), pwd)
		}
		os.MkdirAll(locald, 0755) // Needs to be searchable all the way down.
		runShellProcessOrDie(fmt.Sprintf("cvssync -c -o %s %s", locald, operand), "mirroring")
		makeStub(locald+"/.cvssync", operand)
	} else if exists(operand + "/.cvssync") {
		contents, err := ioutil.ReadFile(operand + "/.cvssync")
		if err != nil {
			croak(operand + "/.cvssync is missing or unreadable")
		}
		runShellProcessOrDie("cvssync -c -o "+operand+" "+string(contents), "mirroring")
	} else if strings.HasPrefix(operand, "git://") || localrepo(operand, "file://", "git") {
		if strings.HasPrefix(operand, "file://") {
			operand = operand[6:]
		}
		if mirrordir != "" {
			locald = mirrordir
		} else {
			locald = tillHash.ReplaceAllString(filepath.Base(operand), pwd)
		}
		runShellProcessOrDie(fmt.Sprintf("git clone -q %s %s", operand, locald), "mirroring")
	} else if isdir(operand + "/.git") {
		under(operand, func() { runShellProcessOrDie("git pull", "mirroring") })
		runShellProcessOrDie(fmt.Sprintf("git clone %s %s", operand, mirrordir), "mirroring")
	} else if strings.HasPrefix(operand, "hg://") || localrepo(operand, "file://", "hg") {
		if strings.HasPrefix(operand, "file://") {
			operand = operand[6:]
		}
		if mirrordir != "" {
			locald = mirrordir
		} else {
			locald = tillHash.ReplaceAllString(filepath.Base(operand), pwd)
		}
		runShellProcessOrDie(fmt.Sprintf("hg clone -q %s %s", operand, locald), "mirroring")
	} else if isdir(operand + "/.hg") {
		under(operand, func() { runShellProcessOrDie("hg update", "mirroring") })
		runShellProcessOrDie(fmt.Sprintf("hg clone %s %s", operand, mirrordir), "mirroring")
	} else {
		croak("%s does not look like a repository mirror.", operand)
	}
}

func tags() string {
	pwd, err := os.Getwd()
	if err != nil {
		log.Fatal(err)
	}
	rt := identifyRepo(".")
	if rt == nil {
		croak("unknown repository type")
	}
	if rt.taglister == "" {
		croak("can't list tags from repository or directory of type %s.", rt.name)
	} else {
		cmd := strings.ReplaceAll(rt.taglister, "${pwd}", pwd)
		return captureFromProcess(cmd, " tag-list command in "+pwd)
	}
	return ""
}

func branches() string {
	pwd, err := os.Getwd()
	if err != nil {
		log.Fatal(err)
	}
	rt := identifyRepo(".")
	if rt == nil {
		croak("unknown repository type")
	}
	if rt.branchlister == "" {
		croak("can't list branches from repository or directory of type %s.", rt.name)
	} else {
		cmd := strings.ReplaceAll(rt.branchlister, "${pwd}", pwd)
		return captureFromProcess(cmd, " branch-list command in "+pwd)
	}
	return ""
}

func checkout(outdir string, rev string) string {
	var err error
	pwd, err := os.Getwd()
	if err != nil {
		log.Fatal(err)
	}
	if nobranch {
		branch = "" // nobranch will also prevent the automatic switch to "trunk"
	}
	if outdir[0] != os.PathSeparator {
		croak("checkout requires absolute target path")
	}
	if exists(outdir) {
		outdir, err = filepath.EvalSymlinks(outdir)
		if err != nil {
			log.Fatal(fmt.Sprintf("chasing symlink: %v", err))
		}
	}
	if verbose {
		fmt.Printf("checkout: from %s to %s\n", pwd, outdir)
	}
	vcs := identifyRepo(".")
	if vcs.name == "cvs" {
		module := captureFromProcess("ls -1 | grep -v CVSROOT", " listing modules")
		if rev != "" {
			rev = "-r " + rev
		}
		// By choosing -kb we get binary files right, but won't
		// suppress any expanded keywords that might be lurking
		// in masters.
		runShellProcessOrDie(fmt.Sprintf("cvs -Q -d:local:%s co -P %s %s %s -d %s -kb %s %s", pwd, branch, tag, rev, outdir, passthrough, module), "checkout")
		return outdir
	} else if vcs.name == "cvs-checkout" {
		runShellProcessOrDie(fmt.Sprintf("cvs -Q -d:local:%s co -P %s %s %s -kb %s", pwd, branch, tag, rev, passthrough), "checkout")
		return outdir
	} else if vcs.name == "svn" {
		if rev != "" {
			rev = "-r " + rev
		}
		/* These options aren't actually documnted */
		username := os.Getenv("RUSERNAME")
		password := os.Getenv("RPASSWORD")
		if username != "" {
			rev += fmt.Sprintf("--username %q", username)
		}
		if password != "" {
			rev += fmt.Sprintf(" --password %q", password)
		}
		// The reason for checkout's odd calling signature -
		// pass it a checkout directory, get back a symlink
		// to what you actually wanted - is here. The problem
		// is that Subversion checkoutd on large repositories
		// are horribly slow.  In case we're doing a
		// comparison on all tags and branches, we want to
		// checlk out the full repo *once* and pass back
		// symlinks to parts in the checkout directory,
		// updating it only as needed. This is is much faster
		// than doing a fresh checkout every time.
		runShellProcessOrDie(fmt.Sprintf("svn co %s -q %s file://%s %s", passthrough, rev, pwd, outdir), "checkout")
		if nobranch {
			// flat repository
		} else if tag != "" {
			outdir = filepath.Join(outdir, "tags", tag)
		} else if branch == "" || branch == "master" || branch == "trunk" {
			outdir = filepath.Join(outdir, "trunk")
		} else if branch != "" {
			outdir = filepath.Join(outdir, "branches", branch)
		}
		return outdir
	} else if vcs.name == "svn-checkout" {
		if rev != "" {
			rev = "-r " + rev
		}
		if passthrough != "" {
			passthrough += " "
		}
		// Potentially dangerous assumption: User made a full checkout
		// of HEAD and the update operation (which is hideously slow on
		// large repositories) only needs to be done if an explicit rev
		// was supplied.
		runShellProcessOrDie("svn up -q "+passthrough+rev, "checkout")
		relpath := ""
		if nobranch {
			// flat repository
		} else if tag != "" && (acceptMissing || isdir("tags")) {
			relpath = filepath.Join("tags", tag)
		} else if (branch == "" || branch == "master" || branch == "trunk") && isdir("trunk") {
			relpath = "trunk"
		} else if branch != "" && isdir(filepath.Join("branches", branch)) {
			relpath = filepath.Join("branches", branch)
		} else if branch != "" && isdir(branch) {
			complain("branch '%s' found at the root which is non-standard", branch)
			relpath = branch
		} else if (branch == "master" || branch == "trunk") && acceptMissing {
			relpath = "trunk"
		} else if branch != "" && acceptMissing {
			relpath = filepath.Join("branches", branch)
		} else {
			croak("invalid branch or tag")
		}
		if exists(outdir) {
			if islink(outdir) {
				os.Remove(outdir)
			} else {
				croak("can't checkout SVN repo to existing %s", outdir)
			}
		}
		part := filepath.Join(pwd, relpath)
		err := os.Symlink(part, outdir)
		if err != nil {
			log.Fatal(err)
		}
		if verbose {
			fmt.Printf("Subversion inward link %s -> %s\n", outdir, part)
		}
		return outdir
	} else if vcs.name == "git" {
		// Only one rev should be given to git checkout
		// Use the passed-in arguments, in some order of specificity.
		handleMissing := false
		if rev == "" {
			if tag != "" {
				rev = tag
			} else if branch != "" {
				rev = branch
			} else {
				rev = "master"
			}
			handleMissing = acceptMissing &&
				(captureFromProcess(fmt.Sprintf("git rev-parse --verify -q %s >/dev/null || echo no", rev), "checkout") != "")
		}
		var path string
		if handleMissing {
			path = pwd + ".git/this/path/does/not/exist"
		} else {
			runShellProcessOrDie(fmt.Sprintf("git checkout --quiet %s %s", passthrough, rev), "checkout")
			path = pwd
		}
		if exists(outdir) {
			if islink(outdir) {
				os.Remove(outdir)
			}
		}
		err := os.Symlink(path, outdir) // to, from
		if err != nil {
			log.Fatal(err)
		}
		if verbose {
			fmt.Printf("Git inward link %s -> %s\n", outdir, path)
		}
		return outdir
	} else if vcs.name == "bzr" {
		croak("checkout is not yet supported in bzr.")
	} else if vcs.name == "brz" {
		croak("checkout is not yet supported in bzr.")
	} else if vcs.name == "hg" {
		spec := ""
		if rev != "" {
			spec = "-r " + rev
		} else if tag != "" {
			spec = "-r " + tag
		} else if branch != "" {
			spec = "-r " + branch
		}
		runShellProcessOrDie(fmt.Sprintf("hg update %s -q %s", passthrough, spec), "checkout")
		if outdir == "." {
			return pwd
		} else if exists(outdir) {
			if islink(outdir) {
				os.Remove(outdir)
			}
		}
		err = os.Symlink(pwd, outdir)
		if err != nil {
			log.Fatal(err)
		}
		if verbose {
			fmt.Printf("Hg inward link %s -> %s\n", outdir, pwd)
		}
		return outdir
	} else if vcs.name == "darcs" {
		croak("checkout is not yet supported for darcs.")
	} else {
		croak("checkout not supported for this repository type.")
	}
	// Empty return indicates error
	return ""
}

// dirlist lists all files and directories under a sprcfief directory.
func dirlist(top string) stringSet {
	outset := newStringSet()
	here, _ := os.Getwd()
	os.Chdir(top)
	filepath.Walk(".", func(path string, info os.FileInfo, err error) error {
		outset.Add(filepath.Clean(path)) // Remove leading ./ if any
		return nil
	})
	os.Chdir(here)
	return outset
}

// ignorable says whether the specified path
func ignorable(filepath string, vcs *VCS) bool {
	// ignorable dotfile
	if path.Base(filepath) == vcs.ignorename {
		return true
	}
	// ignorable checkout subdirectory
	if vcs.checkignore != "" && strings.HasPrefix(filepath, vcs.checkignore+"/") {
		return true
	}
	// ignorable metadata directory
	if strings.HasPrefix(filepath, vcs.subdirectory+"/") {
		return true
	}
	return false
}

// Compare two repositories at a specified revision, defaulting to mainline tip.
func compareRevision(args []string, rev string) string {
	if verbose {
		fmt.Printf("compare: %s\n", args)
	}
	var sourceRev, targetRev string

	if revision != "" {
		vals := strings.Split(revision, ":")
		if len(vals) == 1 {
			sourceRev = vals[0]
			targetRev = vals[0]
		} else if len(vals) == 2 {
			sourceRev = vals[0]
			targetRev = vals[1]
		} else {
			croak("incorrect value for compare -r option.")
		}
	}
	if verbose {
		fmt.Printf("Checkout 1 revision: %s\n", sourceRev)
		fmt.Printf("Checkout 2 revision: %s\n", targetRev)
	}
	if len(args) != 2 {
		croak("compare requires exactly two repository-name args, but there are %v.", args)
	}
	source := args[0]
	target := args[1]
	if !isdir(source) || !isdir(target) {
		croak("both repository directories must exist.")
	}
	TMPDIR := os.Getenv("TMPDIR")
	rsource, err := ioutil.TempDir(TMPDIR, "sourcecheckout")
	if err != nil {
		log.Fatal(err)
	}
	os.RemoveAll(rsource)
	rtarget, err := ioutil.TempDir(TMPDIR, "targetcheckout")
	if err != nil {
		log.Fatal(err)
	}
	os.RemoveAll(rtarget)
	var sourcedir, targetdir string
	under(source, func() {
		sourcedir = checkout(rsource, sourceRev)
		if sourcedir == "" {
			panic("sourcedir unexpectedly nil")
		}
	})
	under(target, func() {
		targetdir = checkout(rtarget, targetRev)
		if targetdir == "" {
			panic("sourcedir unexpectedly nil")
		}
	})
	if acceptMissing {
		if !exists(sourcedir) {
			// replace by empty directory
			os.MkdirAll(sourcedir, 0755)
		}
		if !exists(targetdir) {
			// replace by empty directory
			os.MkdirAll(targetdir, 0755)
		}
	}
	// Ugh.  These are the types of the original repository
	// directories, which in particulat do not imply the ignorables
	// of any corresponding checkout directories.  The obvious way
	// to fix this - run identifyRepo() on the checkout
	// directories sourcedir and targetdir - works for the CVS
	// case but not for the Subversion case.  The problem is that
	// the checkout diectory is a *subdirectory* of the top-level
	// directory where we can expect to find a .svn file.
	sourcetype := identifyRepo(source)
	targettype := identifyRepo(target)
	var diff string
	dollarJunk := regexp.MustCompile(` @\(#\) |\$Id.*\$|\$Header.*\$|$Log.*\$`)
	isDollarLine := func(line string) bool {
		return dollarJunk.MatchString(line)
	}
	sourcefiles := dirlist(sourcedir)
	targetfiles := dirlist(targetdir)
	for _, path := range sourcefiles.Union(targetfiles).Ordered() {
		sourcepath := filepath.Join(sourcedir, path)
		targetpath := filepath.Join(targetdir, path)
		if isdir(sourcepath) || isdir(targetpath) || ignorable(path, sourcetype) || ignorable(path, targettype) {
			continue
		}
		if !targetfiles.Contains(path) {
			diff += fmt.Sprintf("%s: source only\n", path)
			continue
		}
		if !sourcefiles.Contains(path) {
			diff += fmt.Sprintf("%s: target only\n", path)
			continue
		}
		sourceText, err := ioutil.ReadFile(sourcepath)
		if err != nil {
			complain("%s %s is unreadable", sourcetype.name, path)
		}
		targetText, err := ioutil.ReadFile(targetpath)
		if err != nil {
			complain("%s %s is unreadable", targettype.name, path)
		}
		// When this shelled out to diff it had these filters:
		// --ignore-matching-lines=' @(#) '
		// --ignore-matching-lines='$Id.*$'
		// --ignore-matching-lines='$Header.*$'
		// --ignore-matching-lines='$Log.*$'

		if !bytes.Equal(sourceText, targetText) {
			lines0 := difflib.SplitLines(string(sourceText))
			lines1 := difflib.SplitLines(string(targetText))
			file0 := path + " (" + sourcetype.name + ")"
			file1 := path + " (" + targettype.name + ")"
			var text string
			diffObj := difflib.LineDiffParams{
				A:          lines0,
				B:          lines1,
				FromFile:   file0,
				ToFile:     file1,
				Context:    3,
				IsJunkLine: isDollarLine,
			}
			if unified {
				text, _ = difflib.GetUnifiedDiffString(diffObj)
			}
			if context {
				text, _ = difflib.GetContextDiffString(diffObj)
			}
			diff += text
		} else if same {
			diff += fmt.Sprintf("Same: %s\n", path)
		}

		// Check for permission mismatch,  We have to skip directories because
		// of Go MkdirAll's behavior that requiring seek permission; this makes for
		// spurious mismatches in the x permission bit. The error cases here
		// can be reached by symlink entries in Subversion files.
		sstat, err1 := os.Stat(sourcepath)
		if err1 != nil {
			complain("source path stat: %s", err1)
			continue
		}
		tstat, err2 := os.Stat(targetpath)
		if err2 != nil {
			complain("target path stat: %s", err2)
			continue
		}
		if sstat.Mode() != tstat.Mode() {
			diff += fmt.Sprintf("%s: %0o -> %0o\n", path, sstat.Mode(), tstat.Mode())
		}
	}
	os.RemoveAll(rsource)
	os.RemoveAll(rtarget)
	return diff
}

func compareEngine(_singular string, plural string, lister func() string, args []string) string {
	// Compare two repositories at all revisions implied by a specified command.
	if len(args) != 2 {
		croak("compareEngine requires exactly two repository-name arguments, but there are %d %v.", len(args), args)
	}
	source := args[0]
	target := args[1]
	if !isdir(source) || !isdir(target) {
		croak("both repository directories must exist.")
	}
	var sourcerefs, targetrefs []string
	under(source, func() {
		sourcerefs = strings.Fields(strings.TrimSpace(lister()))
	})
	under(target, func() {
		targetrefs = strings.Fields(strings.TrimSpace(lister()))
	})
	common := newStringSet(sourcerefs...).Intersection(newStringSet(targetrefs...))
	sourceonly := newStringSet(sourcerefs...).Subtract(common)
	targetonly := newStringSet(targetrefs...).Subtract(common)
	if refexclude != "" {
		re := regexp.MustCompile(refexclude)
		for k := range sourceonly.store {
			if re.MatchString(k) {
				sourceonly.Remove(k)
			}
		}
		for k := range targetonly.store {
			if re.MatchString(k) {
				targetonly.Remove(k)
			}
		}
	}

	compareResult := ""
	if sourceonly.Len() > 0 {
		compareResult += "----------------------------------------------------------------\n"
		compareResult += fmt.Sprintf("%s only in source:\n", plural)
		for _, item := range sourceonly.Ordered() {
			compareResult += item + "\n"
		}
	}
	if targetonly.Len() > 0 {
		compareResult += "----------------------------------------------------------------\n"
		compareResult += fmt.Sprintf("%s only in target:\n", plural)
		for _, item := range targetonly.Ordered() {
			compareResult += item + "\n"
		}
	}
	if compareResult != "" {
		croak(compareResult)
	}
	report := ""
	if !common.Empty() {
		for _, ref := range common.Ordered() {
			report += compareRevision([]string{source, target}, ref)
		}
	}
	return report
}

func compareTags(args []string) {
	diff := compareEngine("Tag", "Tags", tags, args)
	if diff != "" {
		fmt.Print(diff)
		os.Exit(1)
	} else {
		os.Exit(0)
	}
}

func compareBranches(args []string) {
	diff := compareEngine("Branch", "Branches", branches, args)
	if diff != "" {
		fmt.Print(diff)
		os.Exit(1)
	} else {
		os.Exit(0)
	}
}

func compareAll(args []string) {
	if nobranch {
		if verbose {
			fmt.Print("Comparing the complete repository...")
		}
		compareRevision(args, "")
		return
	}
	if verbose {
		fmt.Print("Comparing master...\n")
	}
	// -a will compare against an empty
	// directory if trunk does not exist, which will thus fail the
	// comparison if it exists on one side but not the other, but
	// will succeed if both repositories have no trunk
	acceptMissing = true
	branch = ""
	diff := compareRevision(args, "")
	if verbose {
		fmt.Print("Comparing tags...")
	}
	diff += compareEngine("Branch", "Branches", branches, args)
	if verbose {
		fmt.Print("Comparing branches...")
	}
	compareBranches(args)
	diff += compareEngine("Branch", "Branches", branches, args)
	if diff != "" {
		fmt.Print(diff)
		os.Exit(1)
	} else {
		os.Exit(0)
	}
}

const dochead = `repotool is a wrapper around repository operations that differ by
version-control system.  It is little use by itself, existing mainly
to generate and simplify a conversion makefile usable with
reposurgeon(1).

Not all actions are supported on all systems.  You will get an
error message and a return value of 1 when attempting an unsupported
action.

With the -v option, report the commands executed just before
they are run. With the -q option, only fatal errors are printed
instead of non-fatal gripes. The -q and -v options also disable each
other and only the last one will take effect.

With the -d option, change to a specified directory before performing
whatever operation was selected. If the directory doesn't exist or
can't be searched into, that's a fatal error.
`

var helpdict = map[string]struct {
	usage    string
	oneliner string
	text     string
}{
	"initialize": {
		"initialize",
		"create Makefile and stub files for standard conversion workflow",
		`The "initialize" option takes a project name (and, optionally,
following source and target VCS types) and generates a
Makefile that will sequence various steps of a repository
conversion. It also generates stub lift and options files. This is
meant to be run in an empty work directory, the tool will refuse
to step on any of these files that already exist.  Afterwards, you
will need to set some variables in the Makefile; read its header
comment.
`},
	"export": {
		"export",
		"export a stream dump of the source repository",
		`The 'export' action, run from within a repository directory,
dumps a copy of a CVS, Subversion, git, bzr, hg, or darcs repository
to a flat history file readable by reposurgeon. The format is usually
a git-fast-import stream, except that Subversion repositories export
as Subversion dump files; the point is to be a lossless
representation, or as close to one as possible.
`},
	"mirror": {
		"mirror {URL|localdir} [localname]",
		"create or update a mirror of the source repository",
		`The 'mirror' action makes or updates a local mirror of a
Subversion, CVS, git, hg, or p4 repo. It requires an argument,
either a repository URL or the name of a local mirror directory
created by a previous run. The first form creates a local mirror of
the repository in a directory named after the last segment of the URL,
with the suffix "-mirror" (the local mirror name can be
overridden by an optional second argument). The second form updates
the local mirror, doing an incremental fetch; just give the mirror
directory name.  If the environment variables RUSERNAME and RPASSWORD
are set, they are used as login/password credentials for Subversion
mirroring.

Subversion URLs are as specified in the public documentation for
Subversion.  CVS URLs must specify a host and repository path,
followed by a '#', followed by a module name.  URLs for git and hg
should be in the form normally used for clone commands.  Perforce
(p4) URLs must specify host, path, and depot (project).

The mirror command can also be passed an rsync URL (service prefix
"rsync://").  This will usually be faster than mirroring through an
equivalent Subversion URL.

Finally, a repository URL may be a "file://" URL, in which
case the repository type is autodetected from the contents of
the indicated directory. Note: A Subversion file URL has *three*
slashes after the "file:" prefix!
`},
	"branches": {
		"branches",
		"list repository branch names",
		`The 'branches' option, run from within a repository directory ,
returns a list of the repository's branch names.
`},
	"checkout": {
		"checkout [-r rev] [-t tag] [-b branch] [-o option]",
		"check out a working copy of the repo",
		`The 'checkout' option checks out a working copy of the
repository. It must be called from within the repository. It takes one
required argument - the checkout directory location.
`},
	"compare": {
		"compare [-r rev] [-t tag] [-b branch] repo1 repo2",
		"compare head content of two repositories",
		`The 'compare' action takes two repository directories. It may
optionally take a tag-branch-revision spec as for the checkout
option. You can also pass two revisions separated by a colon to the -r
option, to have the first one checked out in the first repository and
the second one in the second repository. That permits one to compare
two different revisions, or the same revision referenced differently
in two VCS. You can leave one of the two revisions empty, then the -r
option will not be passed to the corresponding repository checkout.
This is useful to compare a git tag or branch to the corresponding tag
or branch in SVN as seen at a particular revision (specifying both a
branch and revision makes sense in SVN, but not in git).  The selected
versions are compared with diff -r, with noise due to SCCS/RCS/CVS
keyword expansion ignored.  File permissions well as
content are checked, any mismatches will be shown after the diff
listing.
`},
	"compare-tags": {
		"compare-tags repo1 repo2",
		"compare-tags converts content at tags",
		`The 'compare-tags' action takes two repository directories, extracts a
list of tags from the first, then compares the repository contents at
each tag in the list, generating a compare report for each.  Takes
compare options.  Additionally the -e option sets exclude patterns for
tag names that should be ignored.
`},
	"compare-branches": {
		"compare-branches repo1 repo2",
		"compare-branches converts content at branch tips",
		`The 'compare-branches' action takes two repository directories,
extracts a list of branches common to both, then compares the
repository contents at each branch in the list, generating a compare
report for each. Takes compare options.  Additionally the -e option
sets exclude patterns for branch names that should be ignored.
`},
	"compare-all": {
		"compare-all repo1 repo2",
		"run compare, compare-tags, and compare-branches",
		`The 'compare-all' action takes two repository directories, and runs
all three above compare actions on them. Even if the same name is a
tag in one repository and a branch in the other, it will compare them
against each other. Not distinguishing them is useful as CVS tags that
are not applied to every file in the repository may get converted to
branches.  Takes compare options.  Additionally the -e option sets
exclude patterns for tag and branch names that should be ignored.
`},
	"version": {
		"version",
		"report repocutter's version",
		`The "version" command reports the version level of the software.
`},
	"help": {
		"help [command]",
		"emit help about repotool commands",
		`The "help" command displays a summary of commands and options.
With a following argument that is a command name, display detailed help for that command.
`},
}

var narrativeOrder []string = []string{
	"initialize",
	"export",
	"mirror",
	"branches",
	"checkout",
	"compare",
	"compare-tags",
	"compare-branches",
	"compare-all",
	"version",
	"help",
}

func dumpDocs() {
	if len(narrativeOrder) != len(helpdict) {
		os.Stderr.WriteString("repotool: documentation sanity check failed.\n")
		os.Exit(1)
	}
	for _, item := range narrativeOrder {
		os.Stdout.WriteString(item + "::\n")
		text := helpdict[item].text
		text = strings.Replace(text, "\n\n", "\n+\n", -1)
		os.Stdout.WriteString(text)
		os.Stdout.WriteString("\n")
	}
}

func main() {
	flags := flag.NewFlagSet("repotool", flag.ExitOnError)

	flags.BoolVar(&acceptMissing, "a", false, "accept missing trunk directory")
	flags.BoolVar(&context, "c", false, "emit context diff")
	flags.BoolVar(&seeignores, "i", false, "do not suppress comparison of normally ignored directories")
	flags.BoolVar(&nobranch, "n", false, "compare raw structure, ignore SVN branching")
	flags.BoolVar(&quiet, "q", false, "run as quietly as possible")
	flags.BoolVar(&same, "s", false, "show same files")
	flags.BoolVar(&unified, "u", true, "emit unified diff")
	flags.BoolVar(&verbose, "v", false, "show subcommands and diagnostics")

	flags.StringVar(&branch, "b", "", "select branch for checkout or comparison")
	flags.StringVar(&basedir, "d", "", "chdir to the argument repository path before doing checkout")
	flags.StringVar(&refexclude, "e", "", "exclude pattern for tag and branch names.")
	flags.StringVar(&revision, "r", "", "select revision for checkout or comparison")
	flags.StringVar(&tag, "t", "", "select tag for checkout or comparison")
	flags.StringVar(&passthrough, "o", "", "option passthrough")

	if len(os.Args) < 2 {
		fmt.Fprintf(os.Stderr,
			"repotool: requires a subcommand argument - do 'repotool help' for a subcommand list.\n")
		os.Exit(1)
	}
	operation := os.Args[1]

	flags.Parse(os.Args[2:])

	// Suppress progress indicator if output is redirected, not a terminal
	progress = !quiet && term.IsTerminal(int(os.Stdout.Fd()))

	if !strings.HasPrefix(operation, "compare") && (acceptMissing || context || seeignores || same) {
		croak("compare option with non-compare operation, bailing out.")
	}
	if operation != "tag" && operation != "branches" && operation != "checkout" && !strings.HasPrefix(operation, "compare") && refexclude != "" {
		croak("exclusion option with an operation %s that does not accept it", operation)
	}
	if (operation != "checkout" && !strings.HasPrefix(operation, "compare")) && (revision != "" || branch != "" || tag != "") {
		croak("selection option with an operation that is not checkout or compare")
	}

	if basedir != "" {
		if err := os.Chdir(basedir); err != nil {
			croak("changing directory: %v", err)
		}
	}

	args := flags.Args()
	if operation == "initialize" {
		initialize(args)
	} else if operation == "export" {
		export()
	} else if operation == "mirror" {
		mirror(args)
	} else if operation == "tags" {
		os.Stdout.WriteString(tags())
	} else if operation == "branches" {
		os.Stdout.WriteString(branches())
	} else if operation == "checkout" {
		checkout(args[0], revision)
	} else if operation == "compare" {
		if diff := compareRevision(args, revision); diff != "" {
			fmt.Print(diff)
		}
	} else if operation == "compare-tags" {
		compareTags(args)
	} else if operation == "compare-branches" {
		compareBranches(args)
	} else if operation == "compare-all" {
		compareAll(args)
	} else if operation == "version" {
		fmt.Println(version)
	} else if operation == "help" {
		if len(args) == 0 {
			os.Stdout.WriteString(dochead)
			os.Stdout.WriteString("\ncommands:\n")
			keys := make([]string, 0)
			for k := range helpdict {
				keys = append(keys, k)
			}
			sort.Strings(keys)
			for _, key := range keys {
				os.Stdout.WriteString(fmt.Sprintf(" %-16s %s\n", key, helpdict[key].oneliner))
			}
			os.Stdout.WriteString("\noptions:\n")
			flags.PrintDefaults()
		} else if cdoc, ok := helpdict[args[0]]; ok {
			os.Stdout.WriteString(fmt.Sprintf("usage: %s\n\n", cdoc.usage))
			os.Stdout.WriteString(cdoc.text)
		} else {
			croak("no such command\n")
		}
	} else if operation == "docgen" { // Not documented
		dumpDocs()
	} else {
		fmt.Fprintf(os.Stderr, "repotool: unknown operation %q\n", operation)
	}
}

// end
