diff --git a/git-review/branch.go b/git-review/branch.go
index 8c31d8a..c4a44c5 100644
--- a/git-review/branch.go
+++ b/git-review/branch.go
@@ -104,8 +104,7 @@
 var stagedRE = regexp.MustCompile(`^[ACDMR]  `)
 
 func HasStagedChanges() bool {
-	// NOTE: Cannot use getLines, because it throws away leading spaces.
-	for _, s := range strings.Split(getOutput("git", "status", "-b", "--porcelain"), "\n") {
+	for _, s := range getLines("git", "status", "-b", "--porcelain") {
 		if stagedRE.MatchString(s) {
 			return true
 		}
@@ -116,8 +115,7 @@
 var unstagedRE = regexp.MustCompile(`^.[ACDMR]`)
 
 func HasUnstagedChanges() bool {
-	// NOTE: Cannot use getLines, because it throws away leading spaces.
-	for _, s := range strings.Split(getOutput("git", "status", "-b", "--porcelain"), "\n") {
+	for _, s := range getLines("git", "status", "-b", "--porcelain") {
 		if unstagedRE.MatchString(s) {
 			return true
 		}
@@ -128,7 +126,8 @@
 func LocalBranches() []*Branch {
 	var branches []*Branch
 	for _, s := range getLines("git", "branch", "-q") {
-		branches = append(branches, &Branch{Name: strings.TrimPrefix(s, "* ")})
+		s = strings.TrimPrefix(strings.TrimSpace(s), "* ")
+		branches = append(branches, &Branch{Name: s})
 	}
 	return branches
 }
@@ -136,6 +135,7 @@
 func OriginBranches() []string {
 	var branches []string
 	for _, line := range getLines("git", "branch", "-a", "-q") {
+		line = strings.TrimSpace(line)
 		if i := strings.Index(line, " -> "); i >= 0 {
 			line = line[:i]
 		}
diff --git a/git-review/hook.go b/git-review/hook.go
index 7eed33f..f79d78d 100644
--- a/git-review/hook.go
+++ b/git-review/hook.go
@@ -14,11 +14,13 @@
 	"path/filepath"
 	"regexp"
 	"runtime"
+	"strings"
 )
 
 var hookPath = ".git/hooks/"
 var hookFiles = []string{
 	"commit-msg",
+	"pre-commit",
 }
 
 func installHook() {
@@ -93,6 +95,8 @@
 	switch args[0] {
 	case "commit-msg":
 		hookCommitMsg(args[1:])
+	case "pre-commit":
+		hookPreCommit(args[1:])
 	}
 }
 
@@ -135,6 +139,55 @@
 	return regexp.MustCompile(`(?m)^#.*\n`).ReplaceAll(in, nil)
 }
 
+// hookPreCommit is installed as the git pre-commit hook.
+// It prevents commits to the master branch.
+// It checks that the Go files added, copied, or modified by
+// the change are gofmt'd, and if not it prints gofmt instructions
+// and exits with nonzero status.
+func hookPreCommit(args []string) {
+	// Prevent commits to master branches.
+	b := CurrentBranch()
+	if !b.IsLocalOnly() {
+		dief("cannot commit on %s branch", b.Name)
+	}
+
+	root := repoRoot()
+
+	// Run the gofmt check over the pending commit, if any.
+	rev := "HEAD"
+	if b.HasPendingCommit() {
+		rev = "HEAD^" // branch point, hopefully
+	}
+	// This command prints file names relative to the repo root.
+	files := getLines("git", "diff", "--cached", "--name-only", "--diff-filter=ACM", rev)
+	var goFiles []string // absolute paths of files that need gofmting
+	for _, file := range files {
+		if gofmtRequired(file) {
+			goFiles = append(goFiles, filepath.Join(root, file))
+		}
+	}
+	if len(goFiles) == 0 {
+		return
+	}
+
+	// Check gofmt.
+	unfmted := getLines("gofmt", append([]string{"-l"}, goFiles...)...)
+	if len(unfmted) == 0 {
+		return
+	}
+
+	dief("gofmt needs to format these files (run 'git gofmt'):\n\t%s",
+		strings.Join(unfmted, "\n\t"))
+}
+
+// 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 {
+	return strings.HasSuffix(file, ".go") &&
+		!(strings.HasPrefix(file, "test/") && !strings.HasPrefix(file, "test/bench/"))
+}
+
 // This is NOT USED ANYMORE.
 // It is here only for comparing against old commit-hook files.
 var oldCommitMsgHook = `#!/bin/sh
diff --git a/git-review/hook_test.go b/git-review/hook_test.go
index eaa6016..2ccc7c4 100644
--- a/git-review/hook_test.go
+++ b/git-review/hook_test.go
@@ -47,6 +47,38 @@
 	}
 }
 
+func TestHookPreCommit(t *testing.T) {
+	gt := newGitTest(t)
+	defer gt.done()
+
+	gt.removeStubHooks()
+	testMain(t, "hooks") // install hooks
+
+	// Write out a non-Go file.
+	testMain(t, "change", "mybranch")
+	write(t, gt.client+"/msg.txt", "A test message.")
+	trun(t, gt.client, "git", "add", "msg.txt")
+	testMain(t, "hook-invoke", "pre-commit") // should be no-op
+
+	// Write out a badly formatted Go files.
+	if err := os.MkdirAll(gt.client+"/test/bench", 0755); err != nil {
+		t.Fatal(err)
+	}
+	const badGo = "package main\nfunc main(){}"
+	const goodGo = "package main\n\nfunc main() {\n}\n"
+	write(t, gt.client+"/bad.go", badGo)
+	write(t, gt.client+"/good.go", goodGo)
+	write(t, gt.client+"/test/bad.go", badGo)
+	write(t, gt.client+"/test/good.go", goodGo)
+	write(t, gt.client+"/test/bench/bad.go", badGo)
+	write(t, gt.client+"/test/bench/good.go", goodGo)
+	trun(t, gt.client, "git", "add", ".")
+
+	testMainDied(t, "hook-invoke", "pre-commit")
+	testPrintedStderr(t, "gofmt needs to format these files (run 'git gofmt'):",
+		"bad.go", "!good.go", "!test/bad", "test/bench/bad.go")
+}
+
 func TestHooks(t *testing.T) {
 	gt := newGitTest(t)
 	defer gt.done()
@@ -92,6 +124,7 @@
 
 	gt.removeStubHooks()
 	testMain(t, "hooks") // install hooks
+	testMain(t, "change", "mybranch")
 	write(t, gt.client+"/file", "more data")
 	trun(t, gt.client, "git", "add", "file")
 	trun(t, gt.client, "git", "commit", "-m", "mymsg")
diff --git a/git-review/review.go b/git-review/review.go
index 054c510..8f5843c 100644
--- a/git-review/review.go
+++ b/git-review/review.go
@@ -204,7 +204,9 @@
 func getLines(command string, args ...string) []string {
 	var s []string
 	for _, l := range strings.Split(getOutput(command, args...), "\n") {
-		s = append(s, strings.TrimSpace(l))
+		if len(strings.TrimSpace(l)) > 0 {
+			s = append(s, l)
+		}
 	}
 	return s
 }