git-codereview/gofmt.go - review - Git at Google

 // Copyright 2014 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package main

 import (
 	"bytes"
 	"flag"
 	"fmt"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"sort"
 	"strings"
 )

 var gofmtList bool

 func cmdGofmt(args []string) {
 	// NOTE: New flags should be added to the usage message below as well as doc.go.
 	flags.BoolVar(&gofmtList, "l", false, "list files that need to be formatted")
 	flags.Parse(args)
 	if len(flag.Args()) > 0 {
 		fmt.Fprintf(stderr(), "Usage: %s gofmt %s [-l]\n", progName, globalFlags)
 		exit(2)
 	}

 	f := gofmtCommand
 	if !gofmtList {
 		f |= gofmtWrite
 	}

 	files, stderr := runGofmt(f)
 	if gofmtList {
 		w := stdout()
 		for _, file := range files {
 			fmt.Fprintf(w, "%s\n", file)
 		}
 	}
 	if stderr != "" {
 		dief("gofmt reported errors:\n\t%s", strings.Replace(strings.TrimSpace(stderr), "\n", "\n\t", -1))
 	}
 }

 const (
 	gofmtPreCommit = 1 << iota
 	gofmtCommand
 	gofmtWrite
 )

 // runGofmt runs the external gofmt command over modified files.
 //
 // The definition of "modified files" depends on the bit flags.
 // If gofmtPreCommit is set, then runGofmt considers *.go files that
 // differ between the index (staging area) and the branchpoint
 // (the latest commit before the branch diverged from upstream).
 // If gofmtCommand is set, then runGofmt considers all those files
 // in addition to files with unstaged modifications.
 // It never considers untracked files.
 //
 // As a special case for the main repo (but applied everywhere)
 // *.go files under a top-level test directory are excluded from the
 // formatting requirement, except run.go and those in test/bench/.
 //
 // If gofmtWrite is set (only with gofmtCommand, meaning this is 'git gofmt'),
 // runGofmt replaces the original files with their formatted equivalents.
 // Git makes this difficult. In general the file in the working tree
 // (the local file system) can have unstaged changes that make it different
 // from the equivalent file in the index. To help pass the precommit hook,
 // 'git gofmt'  must make it easy to update the files in the index.
 // One option is to run gofmt on all the files of the same name in the
 // working tree and leave it to the user to sort out what should be staged
 // back into the index. Another is to refuse to reformat files for which
 // different versions exist in the index vs the working tree. Both of these
 // options are unsatisfying: they foist busy work onto the user,
 // and it's exactly the kind of busy work that a program is best for.
 // Instead, when runGofmt finds files in the index that need
 // reformatting, it reformats them there, bypassing the working tree.
 // It also reformats files in the working tree that need reformatting.
 // For both, only files modified since the branchpoint are considered.
 // The result should be that both index and working tree get formatted
 // correctly and diffs between the two remain meaningful (free of
 // formatting distractions). Modifying files in the index directly may
 // surprise Git users, but it seems the best of a set of bad choices, and
 // of course those users can choose not to use 'git gofmt'.
 // This is a bit more work than the other git commands do, which is
 // a little worrying, but the choice being made has the nice property
 // that if 'git gofmt' is interrupted, a second 'git gofmt' will put things into
 // the same state the first would have.
 //
 // runGofmt returns a list of files that need (or needed) reformatting.
 // If gofmtPreCommit is set, the names always refer to files in the index.
 // If gofmtCommand is set, then a name without a suffix (see below)
 // refers to both the copy in the index and the copy in the working tree
 // and implies that the two copies are identical. Otherwise, in the case
 // that the index and working tree differ, the file name will have an explicit
 // " (staged)" or " (unstaged)" suffix saying which is meant.
 //
 // runGofmt also returns any standard error output from gofmt,
 // usually indicating syntax errors in the Go source files.
 // If gofmtCommand is set, syntax errors in index files that do not match
 // the working tree show a " (staged)" suffix after the file name.
 // The errors never use the " (unstaged)" suffix, in order to keep
 // references to the local file system in the standard file:line form.
 func runGofmt(flags int) (files []string, stderrText string) {
 	pwd, err := os.Getwd()
 	if err != nil {
 		dief("%v", err)
 	}
 	pwd = filepath.Clean(pwd) // convert to host \ syntax
 	if !strings.HasSuffix(pwd, string(filepath.Separator)) {
 		pwd += string(filepath.Separator)
 	}

 	b := CurrentBranch()
 	repo := repoRoot()
 	if !strings.HasSuffix(repo, string(filepath.Separator)) {
 		repo += string(filepath.Separator)
 	}

 	// Find files modified in the index compared to the branchpoint.
 	// The default of HEAD will only compare against the most recent commit.
 	// But if we know the origin branch, and this isn't a branch tag move,
 	// then check all the pending commits.
 	branchpt := "HEAD"
 	if b.OriginBranch() != "" {
 		isBranchTagMove := strings.Contains(cmdOutput("git", "branch", "-r", "--contains", b.FullName()), "origin/")
 		if !isBranchTagMove {
 			branchpt = b.Branchpoint()
 		}
 	}
 	indexFiles := addRoot(repo, filter(gofmtRequired, nonBlankLines(cmdOutput("git", "diff", "--name-only", "--diff-filter=ACM", "--cached", branchpt, "--"))))
 	localFiles := addRoot(repo, filter(gofmtRequired, nonBlankLines(cmdOutput("git", "diff", "--name-only", "--diff-filter=ACM"))))
 	localFilesMap := stringMap(localFiles)
 	isUnstaged := func(file string) bool {
 		return localFilesMap[file]
 	}

 	if len(indexFiles) == 0 && ((flags&gofmtCommand) == 0 || len(localFiles) == 0) {
 		return
 	}

 	// Determine which files have unstaged changes and are therefore
 	// different from their index versions. For those, the index version must
 	// be copied into a temporary file in the local file system.
 	needTemp := filter(isUnstaged, indexFiles)

 	// Map between temporary file name and place in file tree where
 	// file would be checked out (if not for the unstaged changes).
 	tempToFile := map[string]string{}
 	fileToTemp := map[string]string{}
 	cleanup := func() {} // call before dying (defer won't run)
 	if len(needTemp) > 0 {
 		// Ask Git to copy the index versions into temporary files.
 		// Git stores the temporary files, named .merge_*, in the repo root.
 		// Unlike the Git commands above, the non-temp file names printed
 		// here are relative to the current directory, not the repo root.

 		// git checkout-index --temp is broken on windows. Running this command:
 		//
 		// git checkout-index --temp -- bad-bad-bad2.go bad-bad-broken.go bad-bad-good.go bad-bad2-bad.go bad-bad2-broken.go bad-bad2-good.go bad-broken-bad.go bad-broken-bad2.go bad-broken-good.go bad-good-bad.go bad-good-bad2.go bad-good-broken.go bad2-bad-bad2.go bad2-bad-broken.go bad2-bad-good.go bad2-bad2-bad.go bad2-bad2-broken.go bad2-bad2-good.go bad2-broken-bad.go bad2-broken-bad2.go bad2-broken-good.go bad2-good-bad.go bad2-good-bad2.go bad2-good-broken.go broken-bad-bad2.go broken-bad-broken.go broken-bad-good.go broken-bad2-bad.go broken-bad2-broken.go broken-bad2-good.go
 		//
 		// produces this output
 		//
 		// .merge_file_a05448      bad-bad-bad2.go
 		// .merge_file_b05448      bad-bad-broken.go
 		// .merge_file_c05448      bad-bad-good.go
 		// .merge_file_d05448      bad-bad2-bad.go
 		// .merge_file_e05448      bad-bad2-broken.go
 		// .merge_file_f05448      bad-bad2-good.go
 		// .merge_file_g05448      bad-broken-bad.go
 		// .merge_file_h05448      bad-broken-bad2.go
 		// .merge_file_i05448      bad-broken-good.go
 		// .merge_file_j05448      bad-good-bad.go
 		// .merge_file_k05448      bad-good-bad2.go
 		// .merge_file_l05448      bad-good-broken.go
 		// .merge_file_m05448      bad2-bad-bad2.go
 		// .merge_file_n05448      bad2-bad-broken.go
 		// .merge_file_o05448      bad2-bad-good.go
 		// .merge_file_p05448      bad2-bad2-bad.go
 		// .merge_file_q05448      bad2-bad2-broken.go
 		// .merge_file_r05448      bad2-bad2-good.go
 		// .merge_file_s05448      bad2-broken-bad.go
 		// .merge_file_t05448      bad2-broken-bad2.go
 		// .merge_file_u05448      bad2-broken-good.go
 		// .merge_file_v05448      bad2-good-bad.go
 		// .merge_file_w05448      bad2-good-bad2.go
 		// .merge_file_x05448      bad2-good-broken.go
 		// .merge_file_y05448      broken-bad-bad2.go
 		// .merge_file_z05448      broken-bad-broken.go
 		// error: unable to create file .merge_file_XXXXXX (No error)
 		// .merge_file_XXXXXX      broken-bad-good.go
 		// error: unable to create file .merge_file_XXXXXX (No error)
 		// .merge_file_XXXXXX      broken-bad2-bad.go
 		// error: unable to create file .merge_file_XXXXXX (No error)
 		// .merge_file_XXXXXX      broken-bad2-broken.go
 		// error: unable to create file .merge_file_XXXXXX (No error)
 		// .merge_file_XXXXXX      broken-bad2-good.go
 		//
 		// so limit the number of file arguments to 25.
 		for len(needTemp) > 0 {
 			n := len(needTemp)
 			if n > 25 {
 				n = 25
 			}
 			args := []string{"checkout-index", "--temp", "--"}
 			args = append(args, needTemp[:n]...)
 			// Until Git 2.3.0, git checkout-index --temp is broken if not run in the repo root.
 			// Work around by running in the repo root.
 			// http://article.gmane.org/gmane.comp.version-control.git/261739
 			// https://github.com/git/git/commit/74c4de5
 			for _, line := range nonBlankLines(cmdOutputDir(repo, "git", args...)) {
 				i := strings.Index(line, "\t")
 				if i < 0 {
 					continue
 				}
 				temp, file := line[:i], line[i+1:]
 				temp = filepath.Join(repo, temp)
 				file = filepath.Join(repo, file)
 				tempToFile[temp] = file
 				fileToTemp[file] = temp
 			}
 			needTemp = needTemp[n:]
 		}
 		cleanup = func() {
 			for temp := range tempToFile {
 				os.Remove(temp)
 			}
 			tempToFile = nil
 		}
 		defer cleanup()
 	}
 	dief := func(format string, args ...interface{}) {
 		cleanup()
 		dief(format, args...) // calling top-level dief function
 	}

 	// Run gofmt to find out which files need reformatting;
 	// if gofmtWrite is set, reformat them in place.
 	// For references to local files, remove leading pwd if present
 	// to make relative to current directory.
 	// Temp files and local-only files stay as absolute paths for easy matching in output.
 	args := []string{"-l"}
 	if flags&gofmtWrite != 0 {
 		args = append(args, "-w")
 	}
 	for _, file := range indexFiles {
 		if isUnstaged(file) {
 			args = append(args, fileToTemp[file])
 		} else {
 			args = append(args, strings.TrimPrefix(file, pwd))
 		}
 	}
 	if flags&gofmtCommand != 0 {
 		for _, file := range localFiles {
 			args = append(args, file)
 		}
 	}

 	if *verbose > 1 {
 		fmt.Fprintln(stderr(), commandString("gofmt", args))
 	}
 	cmd := exec.Command("gofmt", args...)
 	var stdout, stderr bytes.Buffer
 	cmd.Stdout = &stdout
 	cmd.Stderr = &stderr
 	err = cmd.Run()

 	if stderr.Len() == 0 && err != nil {
 		// Error but no stderr: usually can't find gofmt.
 		dief("invoking gofmt: %v", err)
 	}

 	// Build file list.
 	files = lines(stdout.String())

 	// Restage files that need to be restaged.
 	if flags&gofmtWrite != 0 {
 		add := []string{"add"}
 		write := []string{"hash-object", "-w", "--"}
 		updateIndex := []string{}
 		for _, file := range files {
 			if real := tempToFile[file]; real != "" {
 				write = append(write, file)
 				updateIndex = append(updateIndex, strings.TrimPrefix(real, repo))
 			} else if !isUnstaged(file) {
 				add = append(add, file)
 			}
 		}
 		if len(add) > 1 {
 			run("git", add...)
 		}
 		if len(updateIndex) > 0 {
 			hashes := nonBlankLines(cmdOutput("git", write...))
 			if len(hashes) != len(write)-3 {
 				dief("git hash-object -w did not write expected number of objects")
 			}
 			var buf bytes.Buffer
 			for i, name := range updateIndex {
 				fmt.Fprintf(&buf, "100644 %s\t%s\n", hashes[i], name)
 			}
 			verbosef("git update-index --index-info")
 			cmd := exec.Command("git", "update-index", "--index-info")
 			cmd.Stdin = &buf
 			out, err := cmd.CombinedOutput()
 			if err != nil {
 				dief("git update-index: %v\n%s", err, out)
 			}
 		}
 	}

 	// Remap temp files back to original names for caller.
 	for i, file := range files {
 		if real := tempToFile[file]; real != "" {
 			if flags&gofmtCommand != 0 {
 				real += " (staged)"
 			}
 			files[i] = strings.TrimPrefix(real, pwd)
 		} else if isUnstaged(file) {
 			files[i] = strings.TrimPrefix(file+" (unstaged)", pwd)
 		}
 	}

 	// Rewrite temp names in stderr, and shorten local file names.
 	// No suffix added for local file names (see comment above).
 	text := "\n" + stderr.String()
 	for temp, file := range tempToFile {
 		if flags&gofmtCommand != 0 {
 			file += " (staged)"
 		}
 		text = strings.Replace(text, "\n"+temp+":", "\n"+strings.TrimPrefix(file, pwd)+":", -1)
 	}
 	for _, file := range localFiles {
 		text = strings.Replace(text, "\n"+file+":", "\n"+strings.TrimPrefix(file, pwd)+":", -1)
 	}
 	text = text[1:]

 	sort.Strings(files)
 	return files, text
 }

 // gofmtRequired reports whether the specified file should be checked
 // for gofmt'dness by the pre-commit hook.
 // The file name is relative to the repo root.
 func gofmtRequired(file string) bool {
 	// TODO: Consider putting this policy into codereview.cfg.
 	if !strings.HasSuffix(file, ".go") {
 		return false
 	}
 	if strings.HasPrefix(file, "vendor/") || strings.Contains(file, "/vendor/") {
 		return false
 	}
 	if strings.HasPrefix(file, "testdata/") || strings.Contains(file, "/testdata/") {
 		return false
 	}
 	if !strings.HasPrefix(file, "test/") {
 		return true
 	}
 	return strings.HasPrefix(file, "test/bench/") || file == "test/run.go"
 }

 // stringMap returns a map m such that m[s] == true if s was in the original list.
 func stringMap(list []string) map[string]bool {
 	m := map[string]bool{}
 	for _, x := range list {
 		m[x] = true
 	}
 	return m
 }

 // filter returns the elements in list satisfying f.
 func filter(f func(string) bool, list []string) []string {
 	var out []string
 	for _, x := range list {
 		if f(x) {
 			out = append(out, x)
 		}
 	}
 	return out
 }

 func addRoot(root string, list []string) []string {
 	var out []string
 	for _, x := range list {
 		out = append(out, filepath.Join(root, x))
 	}
 	return out
 }
	// Copyright 2014 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package main

	import (
	"bytes"
	"flag"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"sort"
	"strings"
	)

	var gofmtList bool

	func cmdGofmt(args []string) {
	// NOTE: New flags should be added to the usage message below as well as doc.go.
	flags.BoolVar(&gofmtList, "l", false, "list files that need to be formatted")
	flags.Parse(args)
	if len(flag.Args()) > 0 {
	fmt.Fprintf(stderr(), "Usage: %s gofmt %s [-l]\n", progName, globalFlags)
	exit(2)
	}

	f := gofmtCommand
	if !gofmtList {
	f \|= gofmtWrite
	}

	files, stderr := runGofmt(f)
	if gofmtList {
	w := stdout()
	for _, file := range files {
	fmt.Fprintf(w, "%s\n", file)
	}
	}
	if stderr != "" {
	dief("gofmt reported errors:\n\t%s", strings.Replace(strings.TrimSpace(stderr), "\n", "\n\t", -1))
	}
	}

	const (
	gofmtPreCommit = 1 << iota
	gofmtCommand
	gofmtWrite
	)

	// runGofmt runs the external gofmt command over modified files.
	//
	// The definition of "modified files" depends on the bit flags.
	// If gofmtPreCommit is set, then runGofmt considers *.go files that
	// differ between the index (staging area) and the branchpoint
	// (the latest commit before the branch diverged from upstream).
	// If gofmtCommand is set, then runGofmt considers all those files
	// in addition to files with unstaged modifications.
	// It never considers untracked files.
	//
	// As a special case for the main repo (but applied everywhere)
	// *.go files under a top-level test directory are excluded from the
	// formatting requirement, except run.go and those in test/bench/.
	//
	// If gofmtWrite is set (only with gofmtCommand, meaning this is 'git gofmt'),
	// runGofmt replaces the original files with their formatted equivalents.
	// Git makes this difficult. In general the file in the working tree
	// (the local file system) can have unstaged changes that make it different
	// from the equivalent file in the index. To help pass the precommit hook,
	// 'git gofmt' must make it easy to update the files in the index.
	// One option is to run gofmt on all the files of the same name in the
	// working tree and leave it to the user to sort out what should be staged
	// back into the index. Another is to refuse to reformat files for which
	// different versions exist in the index vs the working tree. Both of these
	// options are unsatisfying: they foist busy work onto the user,
	// and it's exactly the kind of busy work that a program is best for.
	// Instead, when runGofmt finds files in the index that need
	// reformatting, it reformats them there, bypassing the working tree.
	// It also reformats files in the working tree that need reformatting.
	// For both, only files modified since the branchpoint are considered.
	// The result should be that both index and working tree get formatted
	// correctly and diffs between the two remain meaningful (free of
	// formatting distractions). Modifying files in the index directly may
	// surprise Git users, but it seems the best of a set of bad choices, and
	// of course those users can choose not to use 'git gofmt'.
	// This is a bit more work than the other git commands do, which is
	// a little worrying, but the choice being made has the nice property
	// that if 'git gofmt' is interrupted, a second 'git gofmt' will put things into
	// the same state the first would have.
	//
	// runGofmt returns a list of files that need (or needed) reformatting.
	// If gofmtPreCommit is set, the names always refer to files in the index.
	// If gofmtCommand is set, then a name without a suffix (see below)
	// refers to both the copy in the index and the copy in the working tree
	// and implies that the two copies are identical. Otherwise, in the case
	// that the index and working tree differ, the file name will have an explicit
	// " (staged)" or " (unstaged)" suffix saying which is meant.
	//
	// runGofmt also returns any standard error output from gofmt,
	// usually indicating syntax errors in the Go source files.
	// If gofmtCommand is set, syntax errors in index files that do not match
	// the working tree show a " (staged)" suffix after the file name.
	// The errors never use the " (unstaged)" suffix, in order to keep
	// references to the local file system in the standard file:line form.
	func runGofmt(flags int) (files []string, stderrText string) {
	pwd, err := os.Getwd()
	if err != nil {
	dief("%v", err)
	}
	pwd = filepath.Clean(pwd) // convert to host \ syntax
	if !strings.HasSuffix(pwd, string(filepath.Separator)) {
	pwd += string(filepath.Separator)
	}

	b := CurrentBranch()
	repo := repoRoot()
	if !strings.HasSuffix(repo, string(filepath.Separator)) {
	repo += string(filepath.Separator)
	}

	// Find files modified in the index compared to the branchpoint.
	// The default of HEAD will only compare against the most recent commit.
	// But if we know the origin branch, and this isn't a branch tag move,
	// then check all the pending commits.
	branchpt := "HEAD"
	if b.OriginBranch() != "" {
	isBranchTagMove := strings.Contains(cmdOutput("git", "branch", "-r", "--contains", b.FullName()), "origin/")
	if !isBranchTagMove {
	branchpt = b.Branchpoint()
	}
	}
	indexFiles := addRoot(repo, filter(gofmtRequired, nonBlankLines(cmdOutput("git", "diff", "--name-only", "--diff-filter=ACM", "--cached", branchpt, "--"))))
	localFiles := addRoot(repo, filter(gofmtRequired, nonBlankLines(cmdOutput("git", "diff", "--name-only", "--diff-filter=ACM"))))
	localFilesMap := stringMap(localFiles)
	isUnstaged := func(file string) bool {
	return localFilesMap[file]
	}

	if len(indexFiles) == 0 && ((flags&gofmtCommand) == 0 \|\| len(localFiles) == 0) {
	return
	}

	// Determine which files have unstaged changes and are therefore
	// different from their index versions. For those, the index version must
	// be copied into a temporary file in the local file system.
	needTemp := filter(isUnstaged, indexFiles)

	// Map between temporary file name and place in file tree where
	// file would be checked out (if not for the unstaged changes).
	tempToFile := map[string]string{}
	fileToTemp := map[string]string{}
	cleanup := func() {} // call before dying (defer won't run)
	if len(needTemp) > 0 {
	// Ask Git to copy the index versions into temporary files.
	// Git stores the temporary files, named .merge_*, in the repo root.
	// Unlike the Git commands above, the non-temp file names printed
	// here are relative to the current directory, not the repo root.

	// git checkout-index --temp is broken on windows. Running this command:
	//
	// git checkout-index --temp -- bad-bad-bad2.go bad-bad-broken.go bad-bad-good.go bad-bad2-bad.go bad-bad2-broken.go bad-bad2-good.go bad-broken-bad.go bad-broken-bad2.go bad-broken-good.go bad-good-bad.go bad-good-bad2.go bad-good-broken.go bad2-bad-bad2.go bad2-bad-broken.go bad2-bad-good.go bad2-bad2-bad.go bad2-bad2-broken.go bad2-bad2-good.go bad2-broken-bad.go bad2-broken-bad2.go bad2-broken-good.go bad2-good-bad.go bad2-good-bad2.go bad2-good-broken.go broken-bad-bad2.go broken-bad-broken.go broken-bad-good.go broken-bad2-bad.go broken-bad2-broken.go broken-bad2-good.go
	//
	// produces this output
	//
	// .merge_file_a05448 bad-bad-bad2.go
	// .merge_file_b05448 bad-bad-broken.go
	// .merge_file_c05448 bad-bad-good.go
	// .merge_file_d05448 bad-bad2-bad.go
	// .merge_file_e05448 bad-bad2-broken.go
	// .merge_file_f05448 bad-bad2-good.go
	// .merge_file_g05448 bad-broken-bad.go
	// .merge_file_h05448 bad-broken-bad2.go
	// .merge_file_i05448 bad-broken-good.go
	// .merge_file_j05448 bad-good-bad.go
	// .merge_file_k05448 bad-good-bad2.go
	// .merge_file_l05448 bad-good-broken.go
	// .merge_file_m05448 bad2-bad-bad2.go
	// .merge_file_n05448 bad2-bad-broken.go
	// .merge_file_o05448 bad2-bad-good.go
	// .merge_file_p05448 bad2-bad2-bad.go
	// .merge_file_q05448 bad2-bad2-broken.go
	// .merge_file_r05448 bad2-bad2-good.go
	// .merge_file_s05448 bad2-broken-bad.go
	// .merge_file_t05448 bad2-broken-bad2.go
	// .merge_file_u05448 bad2-broken-good.go
	// .merge_file_v05448 bad2-good-bad.go
	// .merge_file_w05448 bad2-good-bad2.go
	// .merge_file_x05448 bad2-good-broken.go
	// .merge_file_y05448 broken-bad-bad2.go
	// .merge_file_z05448 broken-bad-broken.go
	// error: unable to create file .merge_file_XXXXXX (No error)
	// .merge_file_XXXXXX broken-bad-good.go
	// error: unable to create file .merge_file_XXXXXX (No error)
	// .merge_file_XXXXXX broken-bad2-bad.go
	// error: unable to create file .merge_file_XXXXXX (No error)
	// .merge_file_XXXXXX broken-bad2-broken.go
	// error: unable to create file .merge_file_XXXXXX (No error)
	// .merge_file_XXXXXX broken-bad2-good.go
	//
	// so limit the number of file arguments to 25.
	for len(needTemp) > 0 {
	n := len(needTemp)
	if n > 25 {
	n = 25
	}
	args := []string{"checkout-index", "--temp", "--"}
	args = append(args, needTemp[:n]...)
	// Until Git 2.3.0, git checkout-index --temp is broken if not run in the repo root.
	// Work around by running in the repo root.
	// http://article.gmane.org/gmane.comp.version-control.git/261739
	// https://github.com/git/git/commit/74c4de5
	for _, line := range nonBlankLines(cmdOutputDir(repo, "git", args...)) {
	i := strings.Index(line, "\t")
	if i < 0 {
	continue
	}
	temp, file := line[:i], line[i+1:]
	temp = filepath.Join(repo, temp)
	file = filepath.Join(repo, file)
	tempToFile[temp] = file
	fileToTemp[file] = temp
	}
	needTemp = needTemp[n:]
	}
	cleanup = func() {
	for temp := range tempToFile {
	os.Remove(temp)
	}
	tempToFile = nil
	}
	defer cleanup()
	}
	dief := func(format string, args ...interface{}) {
	cleanup()
	dief(format, args...) // calling top-level dief function
	}

	// Run gofmt to find out which files need reformatting;
	// if gofmtWrite is set, reformat them in place.
	// For references to local files, remove leading pwd if present
	// to make relative to current directory.
	// Temp files and local-only files stay as absolute paths for easy matching in output.
	args := []string{"-l"}
	if flags&gofmtWrite != 0 {
	args = append(args, "-w")
	}
	for _, file := range indexFiles {
	if isUnstaged(file) {
	args = append(args, fileToTemp[file])
	} else {
	args = append(args, strings.TrimPrefix(file, pwd))
	}
	}
	if flags&gofmtCommand != 0 {
	for _, file := range localFiles {
	args = append(args, file)
	}
	}

	if *verbose > 1 {
	fmt.Fprintln(stderr(), commandString("gofmt", args))
	}
	cmd := exec.Command("gofmt", args...)
	var stdout, stderr bytes.Buffer
	cmd.Stdout = &stdout
	cmd.Stderr = &stderr
	err = cmd.Run()

	if stderr.Len() == 0 && err != nil {
	// Error but no stderr: usually can't find gofmt.
	dief("invoking gofmt: %v", err)
	}

	// Build file list.
	files = lines(stdout.String())

	// Restage files that need to be restaged.
	if flags&gofmtWrite != 0 {
	add := []string{"add"}
	write := []string{"hash-object", "-w", "--"}
	updateIndex := []string{}
	for _, file := range files {
	if real := tempToFile[file]; real != "" {
	write = append(write, file)
	updateIndex = append(updateIndex, strings.TrimPrefix(real, repo))
	} else if !isUnstaged(file) {
	add = append(add, file)
	}
	}
	if len(add) > 1 {
	run("git", add...)
	}
	if len(updateIndex) > 0 {
	hashes := nonBlankLines(cmdOutput("git", write...))
	if len(hashes) != len(write)-3 {
	dief("git hash-object -w did not write expected number of objects")
	}
	var buf bytes.Buffer
	for i, name := range updateIndex {
	fmt.Fprintf(&buf, "100644 %s\t%s\n", hashes[i], name)
	}
	verbosef("git update-index --index-info")
	cmd := exec.Command("git", "update-index", "--index-info")
	cmd.Stdin = &buf
	out, err := cmd.CombinedOutput()
	if err != nil {
	dief("git update-index: %v\n%s", err, out)
	}
	}
	}

	// Remap temp files back to original names for caller.
	for i, file := range files {
	if real := tempToFile[file]; real != "" {
	if flags&gofmtCommand != 0 {
	real += " (staged)"
	}
	files[i] = strings.TrimPrefix(real, pwd)
	} else if isUnstaged(file) {
	files[i] = strings.TrimPrefix(file+" (unstaged)", pwd)
	}
	}

	// Rewrite temp names in stderr, and shorten local file names.
	// No suffix added for local file names (see comment above).
	text := "\n" + stderr.String()
	for temp, file := range tempToFile {
	if flags&gofmtCommand != 0 {
	file += " (staged)"
	}
	text = strings.Replace(text, "\n"+temp+":", "\n"+strings.TrimPrefix(file, pwd)+":", -1)
	}
	for _, file := range localFiles {
	text = strings.Replace(text, "\n"+file+":", "\n"+strings.TrimPrefix(file, pwd)+":", -1)
	}
	text = text[1:]

	sort.Strings(files)
	return files, text
	}

	// gofmtRequired reports whether the specified file should be checked
	// for gofmt'dness by the pre-commit hook.
	// The file name is relative to the repo root.
	func gofmtRequired(file string) bool {
	// TODO: Consider putting this policy into codereview.cfg.
	if !strings.HasSuffix(file, ".go") {
	return false
	}
	if strings.HasPrefix(file, "vendor/") \|\| strings.Contains(file, "/vendor/") {
	return false
	}
	if strings.HasPrefix(file, "testdata/") \|\| strings.Contains(file, "/testdata/") {
	return false
	}
	if !strings.HasPrefix(file, "test/") {
	return true
	}
	return strings.HasPrefix(file, "test/bench/") \|\| file == "test/run.go"
	}

	// stringMap returns a map m such that m[s] == true if s was in the original list.
	func stringMap(list []string) map[string]bool {
	m := map[string]bool{}
	for _, x := range list {
	m[x] = true
	}
	return m
	}

	// filter returns the elements in list satisfying f.
	func filter(f func(string) bool, list []string) []string {
	var out []string
	for _, x := range list {
	if f(x) {
	out = append(out, x)
	}
	}
	return out
	}

	func addRoot(root string, list []string) []string {
	var out []string
	for _, x := range list {
	out = append(out, filepath.Join(root, x))
	}
	return out
	}