checkout/checkout.go

// Copyright 2019 The Fuchsia 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 checkout

import (
	"context"
	"fmt"
	"io"
	"net/url"
	"os"
	"strings"

	buildbucketpb "go.chromium.org/luci/buildbucket/proto"
	"go.fuchsia.dev/infra/execution"
)

const gitFatalLogPrefix = "fatal: "

// Checkout checks out the git repo at repoURL according to the given build
// input.
//
// defaultRevision specifies the revision to check out if the build was
// triggered by a commit or change on a *different* repository, in which case we
// can't use the build input to determine which revision of `repoURL` to check
// out.
func Checkout(ctx context.Context, input *buildbucketpb.Build_Input, repoURL url.URL, defaultRevision, dir string) error {
	strat, err := newStrategy(input, repoURL, defaultRevision)
	if err != nil {
		return err
	}

	var stderrBuf strings.Builder
	stderrWriter := io.MultiWriter(os.Stderr, &stderrBuf)
	// Write everything to stderr. luciexe expects the stdout of the
	// recipe_bootstrap tool to be a proto.
	executor := execution.NewExecutor(os.Stderr, stderrWriter, dir)
	if err := strat.Checkout(ctx, executor); err != nil {
		// When git fails it usually emits a "fatal" log in the last line of
		// stderr. Make a best effort at parsing out that line and including it in
		// the error message.
		lines := strings.Split(strings.TrimSpace(stderrBuf.String()), "\n")
		lastLine := lines[len(lines)-1]
		if strings.HasPrefix(lastLine, gitFatalLogPrefix) {
			return fmt.Errorf("%s. Original error: %w", strings.TrimPrefix(lastLine, gitFatalLogPrefix), err)
		}
		return err
	}
	return nil
}