deploytool: Add README.md, migrate docs to it.

deploytool/cmd/luci_deploy/checkout.go

 // Copyright 2016 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package main
 
 import (
         "crypto/sha256"
         "encoding/hex"
         "fmt"
         "net/url"
         "os"
         "path/filepath"
         "sort"
         "strconv"
         "strings"
 
         "github.com/luci/luci-go/common/cli"
         "github.com/luci/luci-go/common/errors"
         log "github.com/luci/luci-go/common/logging"
         "github.com/luci/luci-go/deploytool/api/deploy"
         "github.com/luci/luci-go/deploytool/managedfs"
 
         "github.com/maruel/subcommands"
 )
 
 // deployToolCfg is the name of the source-root deployment configuration file.
 const (
         // deployToolCfg is the name of the source-root deploytool configuration file.
-        deployToolCfg = ".luci-deploytool.cfg"
+        deployToolCfg = "luci-deploy.cfg"
 
         // checkoutsSubdir is the name of the checkouts directory underneath the
         // working directory.
         checkoutsSubdir = "checkouts"
         // frozenCheckoutName is the name in the checkout directory of the frozen
         // checkout file.
         frozenCheckoutName = "checkout.frozen.cfg"
 
         // gitMajorVersionSize it the number of characters from the Git revision hash
         // to use for its major version.
@@ skipping 97 matching lines @@
 
                         // If we're overriding sources, and this source is overridden, then apply
                         // this and add the overriding source to the registry as well.
                         //
                         // We will still keep the original source in the registry so it doesn't
                         // get deleted during cleanup.
                         if applyOverrides {
                                 if override, ok := l.userSourceOverrides[sc.overrideURL]; ok {
                                         log.Infof(w, "Applying user repository override: [%+v] => [%+v]", sc.Source, override)
 
+                                        // Any local overrides cause the source group to be considered
+                                        // tainted.
                                         sc.FrozenLayout_Source.Source = override
+                                        sc.FrozenLayout_Source.Source.Tainted = true
+
                                         if err := sc.addRegistryRepos(&reg); err != nil {
                                                 return errors.Annotate(err).Reason("failed to add (overridden) [%(sourceCheckout)s] to registry").
                                                         D("sourceCheckout", sc).Err()
                                         }
                                 }
                         }
 
                         groupSrcs[i] = &sc
                         scs = append(scs, &sc)
                 }
@@ skipping 507 matching lines @@
                                 return errors.Annotate(err).Reason("failed to stat SourceInitResult [%(resultPath)s]").
                                         D("resultPath", resultPath).Err()
                         }
                 })
                 return &r, err
 
         default:
                 return nil, errors.Reason("unknown source init type %(type)T").D("type", t).Err()
         }
 }