Add object-map option to get a map from the old sha1 to new sha1

#2766

commands/command_migrate.go

@@ -32,6 +32,10 @@ var (
 
 	// migrateVerbose enables verbose logging
 	migrateVerbose bool
+
+	// objectMapFile is the path to the map of old sha1 to new sha1
+	// commits
+	objectMapFilePath string
 )
 
 // migrate takes the given command and arguments, *odb.ObjectDatabase, as well
@@ -83,8 +87,9 @@ func rewriteOptions(args []string, opts *githistory.RewriteOptions, l *tasklog.L
 		Include: include,
 		Exclude: exclude,
 
-		UpdateRefs: opts.UpdateRefs,
-		Verbose:    opts.Verbose,
+		UpdateRefs:        opts.UpdateRefs,
+		Verbose:           opts.Verbose,
+		ObjectMapFilePath: opts.ObjectMapFilePath,
 
 		BlobFn:         opts.BlobFn,
 		TreeCallbackFn: opts.TreeCallbackFn,
@@ -281,6 +286,7 @@ func init() {
 
 	importCmd := NewCommand("import", migrateImportCommand)
 	importCmd.Flags().BoolVar(&migrateVerbose, "verbose", false, "Verbose logging")
+	importCmd.Flags().StringVar(&objectMapFilePath, "object-map", "", "Object map file")
 
 	RegisterCommand("migrate", nil, func(cmd *cobra.Command) {
 		cmd.PersistentFlags().StringVarP(&includeArg, "include", "I", "", "Include a list of paths")

commands/command_migrate_import.go

@@ -36,7 +36,8 @@ func migrateImportCommand(cmd *cobra.Command, args []string) {
 	gitfilter := lfs.NewGitFilter(cfg)
 
 	migrate(args, rewriter, l, &githistory.RewriteOptions{
-		Verbose: migrateVerbose,
+		Verbose:           migrateVerbose,
+		ObjectMapFilePath: objectMapFilePath,
 		BlobFn: func(path string, b *odb.Blob) (*odb.Blob, error) {
 			if filepath.Base(path) == ".gitattributes" {
 				return b, nil

git/githistory/rewriter.go

@@ -54,6 +54,10 @@ type RewriteOptions struct {
 	// Verbose mode prints migrated objects.
 	Verbose bool
 
+	// ObjectMapFilePath is the path to the map of old sha1 to new sha1
+	// commits
+	ObjectMapFilePath string
+
 	// BlobFn specifies a function to rewrite blobs.
 	//
 	// It is called once per unique, unchanged path. That is to say, if
@@ -188,6 +192,15 @@ func (r *Rewriter) Rewrite(opt *RewriteOptions) ([]byte, error) {
 		vPerc = perc
 	}
 
+	var objectMapFile *os.File
+	if len(opt.ObjectMapFilePath) > 0 {
+		objectMapFile, err = os.Create(opt.ObjectMapFilePath)
+		if err != nil {
+			return nil, fmt.Errorf("Could not create object map file: %v", err)
+		}
+		defer objectMapFile.Close()
+	}
+
 	// Keep track of the last commit that we rewrote. Callers often want
 	// this so that they can perform a git-update-ref(1).
 	var tip []byte
@@ -253,6 +266,13 @@ func (r *Rewriter) Rewrite(opt *RewriteOptions) ([]byte, error) {
 			if err != nil {
 				return nil, err
 			}
+			if len(opt.ObjectMapFilePath) > 0 {
+				mapStr := fmt.Sprintf("%s,%s\n", hex.EncodeToString(oid), hex.EncodeToString(newSha))
+				_, err := objectMapFile.WriteString(mapStr)
+				if err != nil {
+					return nil, err
+				}
+			}
 		}
 
 		// Cache that commit so that we can reassign children of this

test/test-migrate-import.sh

@@ -616,3 +616,20 @@ begin_test "migrate import (handle copies of files)"
   [ "$oid_root" = "$oid_root_after_migration" ]
 )
 end_test
+
+begin_test "migrate import (--object-map)"
+(
+  set -e
+
+  setup_multiple_local_branches
+
+  output_dir=$(mktemp -d)
+
+  git log --all --pretty='format:%H' > "${output_dir}/old_sha.txt"
+  git lfs migrate import --everything --object-map "${output_dir}/object-map.txt"
+  git log --all --pretty='format:%H' > "${output_dir}/new_sha.txt"
+  paste -d',' "${output_dir}/old_sha.txt" "${output_dir}/new_sha.txt" > "${output_dir}/expected-map.txt"
+
+  diff -u "${output_dir}/expected-map.txt" "${output_dir}/object-map.txt"
+)
+end_test