Merge pull request #213 from google/dvyukov-git

pkg/git: add new package

2 files changed, 90 insertions, 45 deletions

diff --git a/pkg/git/git.go b/pkg/git/git.go
new file mode 100644
index 000000000..773535cb7
--- /dev/null
+++ b/pkg/git/git.go
@@ -0,0 +1,86 @@
+// Copyright 2017 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+// Package git provides helper functions for working with git repositories.
+package git
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"os/exec"
+	"time"
+)
+
+// Poll checkouts the specified repository/branch in dir.
+// This involves fetching/resetting/cloning as necessary to recover from all possible problems.
+// Returns hash of the HEAD commit in the specified branch.
+func Poll(dir, repo, branch string) (string, error) {
+	runCmd(dir, "git", "reset", "--hard")
+	if _, err := runCmd(dir, "git", "fetch", "--no-tags", "--depth=", "1"); err != nil {
+		if err := os.RemoveAll(dir); err != nil {
+			return "", fmt.Errorf("failed to remove repo dir: %v", err)
+		}
+		if err := os.MkdirAll(dir, 0700); err != nil {
+			return "", fmt.Errorf("failed to create repo dir: %v", err)
+		}
+		args := []string{
+			"clone",
+			repo,
+			"--no-tags",
+			"--depth", "1",
+			"--single-branch",
+			"--branch", branch,
+			dir,
+		}
+		if _, err := runCmd("", "git", args...); err != nil {
+			return "", err
+		}
+	}
+	if _, err := runCmd(dir, "git", "checkout", branch); err != nil {
+		return "", err
+	}
+	return HeadCommit(dir)
+}
+
+// HeadCommit returns hash of the HEAD commit of the current branch of git repository in dir.
+func HeadCommit(dir string) (string, error) {
+	output, err := runCmd(dir, "git", "log", "--pretty=format:'%H'", "-n", "1")
+	if err != nil {
+		return "", err
+	}
+	if len(output) != 0 && output[len(output)-1] == '\n' {
+		output = output[:len(output)-1]
+	}
+	if len(output) != 0 && output[0] == '\'' && output[len(output)-1] == '\'' {
+		output = output[1 : len(output)-1]
+	}
+	if len(output) != 40 {
+		return "", fmt.Errorf("unexpected git log output, want commit hash: %q", output)
+	}
+	return string(output), nil
+}
+
+func runCmd(dir, bin string, args ...string) ([]byte, error) {
+	output := new(bytes.Buffer)
+	cmd := exec.Command(bin, args...)
+	cmd.Dir = dir
+	cmd.Stdout = output
+	cmd.Stderr = output
+	if err := cmd.Start(); err != nil {
+		return nil, fmt.Errorf("failed to start %v %+v: %v", bin, args, err)
+	}
+	done := make(chan bool)
+	go func() {
+		select {
+		case <-time.After(time.Hour):
+			cmd.Process.Kill()
+		case <-done:
+		}
+	}()
+	defer close(done)
+	if err := cmd.Wait(); err != nil {
+		return nil, fmt.Errorf("failed to run %v %+v: %v\n%v", bin, args, err, output.String())
+	}
+	return output.Bytes(), nil
+}
diff --git a/syz-gce/syz-gce.go b/syz-gce/syz-gce.go
index 9bdedbe5b..ddc410536 100644
--- a/syz-gce/syz-gce.go
+++ b/syz-gce/syz-gce.go
@@ -42,6 +42,7 @@ import (
 	"github.com/google/syzkaller/gce"
 	. "github.com/google/syzkaller/log"
 	pkgconfig "github.com/google/syzkaller/pkg/config"
+	"github.com/google/syzkaller/pkg/git"
 	"github.com/google/syzkaller/syz-manager/config"
 	"golang.org/x/net/context"
 )
@@ -302,7 +303,7 @@ func (a *SyzkallerAction) Poll() (string, error) {
 	if _, err := runCmd("", "go", "get", "-u", "-d", "github.com/google/syzkaller/syz-manager"); err != nil {
 		return "", err
 	}
-	return gitRevision("gopath/src/github.com/google/syzkaller")
+	return git.HeadCommit("gopath/src/github.com/google/syzkaller")
 }
 
 func (a *SyzkallerAction) Build() error {
@@ -346,32 +347,7 @@ func (a *LocalBuildAction) Name() string {
 
 func (a *LocalBuildAction) Poll() (string, error) {
 	dir := filepath.Join(a.Dir, "linux")
-	runCmd(dir, "git", "reset", "--hard")
-	if _, err := runCmd(dir, "git", "pull"); err != nil {
-		if err := os.RemoveAll(dir); err != nil {
-			return "", fmt.Errorf("failed to remove repo dir: %v", err)
-		}
-		if err := os.MkdirAll(dir, 0700); err != nil {
-			return "", fmt.Errorf("failed to create repo dir: %v", err)
-		}
-		cloneArgs := []string{"clone", a.Repo, "--single-branch", "--depth", "1"}
-		if a.Branch != "" {
-			cloneArgs = append(cloneArgs, "--branch", a.Branch)
-		}
-		cloneArgs = append(cloneArgs, dir)
-		if _, err := runCmd("", "git", cloneArgs...); err != nil {
-			return "", err
-		}
-		if _, err := runCmd(dir, "git", "pull"); err != nil {
-			return "", err
-		}
-	}
-	if a.Branch != "" {
-		if _, err := runCmd(dir, "git", "checkout", a.Branch); err != nil {
-			return "", err
-		}
-	}
-	rev, err := gitRevision(dir)
+	rev, err := git.Poll(dir, a.Repo, a.Branch)
 	if err != nil {
 		return "", err
 	}
@@ -383,7 +359,7 @@ func (a *LocalBuildAction) Poll() (string, error) {
 
 func (a *LocalBuildAction) Build() error {
 	dir := filepath.Join(a.Dir, "linux")
-	hash, err := gitRevision(dir)
+	hash, err := git.HeadCommit(dir)
 	if err != nil {
 		return err
 	}
@@ -633,23 +609,6 @@ func uploadFile(localFile, gcsFile string) error {
 	return nil
 }
 
-func gitRevision(dir string) (string, error) {
-	output, err := runCmd(dir, "git", "log", "--pretty=format:'%H'", "-n", "1")
-	if err != nil {
-		return "", err
-	}
-	if len(output) != 0 && output[len(output)-1] == '\n' {
-		output = output[:len(output)-1]
-	}
-	if len(output) != 0 && output[0] == '\'' && output[len(output)-1] == '\'' {
-		output = output[1 : len(output)-1]
-	}
-	if len(output) != 40 {
-		return "", fmt.Errorf("unexpected git log output, want commit hash: %q", output)
-	}
-	return string(output), nil
-}
-
 func buildKernel(dir, ccompiler string) error {
 	os.Remove(filepath.Join(dir, ".config"))
 	if _, err := runCmd(dir, "make", "defconfig"); err != nil {