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// Copyright 2017 The Chromium 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 (
// Replace clock_gettime for OSX 10.11.
_ ""
// versionString is the version string for this wrapper.
// It is displayed by augmenting Git's "version" subcommand output.
var versionString = probeVersionString()
// gitWrapperErrorReturnCode is a return code used by the Git wrapper to
// indicate a Git wrapper failure. It is intended to try and distinguish itself
// from an actual Git return code, which tend to start at 1.
const gitWrapperErrorReturnCode = 250
// gitWrapperENV is set for delegate processes both to indicate that they are
// being run within a Git wrapper and to track Git state.State.
const gitWrapperENV = "INFRA_GIT_WRAPPER"
// gitWrapperCheckENV is set to instruct delegate processes to perform a Git
// wrapper check.
// If a Git wrapper process observes this environment variable, it must exit
// immediately with a non-zero return code.
const gitWrapperCheckENV = "INFRA_GIT_WRAPPER_CHECK"
// gitWrapperTraceENV, if set and not empty, instructs the Git wrapper to emit
// trace-level logging.
// NOTE: This can get in the way of some processes that require output parsing.
const gitWrapperTraceENV = "INFRA_GIT_WRAPPER_TRACE"
// gitWrapperHomeENV, if set and not empty, instructs Git wrapper to substitute
// HOME with given value when calling git. Setting it to empty string removes
// HOME env var completely. Useful for overriding global git configs.
const gitWrapperHomeENV = "INFRA_GIT_WRAPPER_HOME"
// gitProbe is the SystemProbe used by the main application to locate Git.
var gitProbe = SystemProbe{
Target: "git",
RelativePathOverride: []string{"bin"},
// probeVersionString attempts to identify the version string for the current
// package.
// It is determined by probing the package's CIPD metadata, and will default to
// "Unknown" if the package is either not installed via CIPD or has invalid
// metadata.
func probeVersionString() string {
info, err := version.GetStartupVersion()
if err == nil && info.PackageName != "" && info.InstanceID != "" {
return fmt.Sprintf("%s @ %s", info.PackageName, info.InstanceID)
return "Unknown Version"
func mainImpl(c context.Context, argv []string, env environ.Env, stdin io.Reader, stdout, stderr io.Writer) int {
// Set up our logging parameters. If we're not tracing, we will only show
// Info and higher level logs.
const loggingFormat = `[%{level:.1s} %{shortfile}] %{message}`
logCfg := gologger.LoggerConfig{
Out: os.Stderr,
Format: loggingFormat,
c = logCfg.Use(c)
if v, _ := env.Get(gitWrapperTraceENV); v != "" {
c = logging.SetLevel(c, logging.Debug)
} else {
c = logging.SetLevel(c, logging.Info)
// If we are performing a Git wrapper check, exit immediately with a non-zero
// return code.
if _, ok := env.Get(gitWrapperCheckENV); ok {
logging.Debugf(c, "Observed check env ["+gitWrapperCheckENV+"]; exiting with non-zero code.")
return 1
// Check if we are being passed a wrapper state.
var st state.State
if v, ok := env.Get(gitWrapperENV); ok {
if err := st.FromENV(v); err != nil {
logging.Warningf(c, "Failed to decode "+gitWrapperENV+" [%s]: %s", v, err)
logging.Debugf(c, "Loaded state from ["+gitWrapperENV+"]: %#v", st)
// Locate the system Git.
err := gitProbe.ResolveSelf(argv[0])
logging.Debugf(c, "Identified Git wrapper (self) path at: %s", gitProbe.self)
switch {
case err != nil:
// If we can't identify our own path, we can't check our cached Git path,
// so invalidate it.
logging.Warningf(c, "Failed to get absolute path of self [%s]: %s", gitProbe.self, err)
st.SelfPath = ""
st.GitPath = ""
case gitProbe.self != st.SelfPath:
// The wrapper state either doesn't have a "self" path, or was built by some
// other wrapper. Invalidate its Git state and update its "self".
st.GitPath = ""
st.SelfPath = gitProbe.self
if st.GitPath, err = gitProbe.Locate(c, st.GitPath, env); err != nil {
errors.Log(c, errors.Annotate(err, "failed to locate system Git").Err())
return gitWrapperErrorReturnCode
logging.Debugf(c, "Identified system Git at: %s", st.GitPath)
// Setup custom HOME, if requested. This makes git lookup .gitconfig and
// .netrc there instead of default '~'.
if newHome, ok := env.Get(gitWrapperHomeENV); ok {
if newHome != "" {
env.Set("HOME", newHome)
} else {
// Construct and execute a managed Git command.
cmd := GitCommand{
State: st,
LowSpeedLimit: 1000,
LowSpeedTime: 5 * time.Minute,
RetryList: []*regexp.Regexp{DefaultGitRetryRegexp},
Retry: gitTransientRetry,
Stdin: stdin,
Stdout: stdout,
Stderr: stderr,
rc, err := cmd.Run(c, argv[1:], env)
if err != nil {
errors.Log(c, errors.Annotate(err, "failed to run Git").Err())
return gitWrapperErrorReturnCode
return rc
// gitTransientRetry returns the retry.Iterator to use when retrying Git
// transient failures.
// We want the retry to be fastish, but not so fast that it overwhelms or
// exacerbates the remote problem. Google Git engineers have requested a
// longer initial backoff (rather than a few milliseconds).
func gitTransientRetry() retry.Iterator {
delay := time.Duration(rand.Float64() + 2.5)
return &retry.ExponentialBackoff{
Limited: retry.Limited{
Delay: delay * time.Second,
Retries: 12,
Multiplier: 1.5,
func main() {
os.Exit(mainImpl(context.Background(), os.Args, environ.System(), nil, nil, nil))