1 files changed, 86 insertions, 0 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
+}