feat(cmd): Make "extract" arguments mroe closely mirror common archive tools (#653)

Usage: car extract --file file.car [--output output] [mydir/mysubdir] [mydir/mysubdir2/file] [mydir2] [myfile]...

This also makes "extract" much more consistent with "create" and matching common archive tools:

- Not specifying any paths results in a complete extraction.
- To read from stdin a single dash ('-') is specified as the input file.

Author: davidebeatrici

cmd/car/car.go

@@ -100,23 +100,21 @@ func main1() int {
 				}},
 			},
 			{
-				Name:      "extract",
-				Aliases:   []string{"x"},
-				Usage:     "Extract the contents of a car when the car encodes UnixFS data",
-				Action:    ExtractCar,
-				ArgsUsage: "[output directory|-]",
+				Name:    "extract",
+				Aliases: []string{"x"},
+				Usage:   "Extract the contents of a car when the car encodes UnixFS data",
+				Action:  ExtractCar,
 				Flags: []cli.Flag{
 					&cli.StringFlag{
 						Name:      "file",
-						Aliases:   []string{"f"},
-						Usage:     "The car file to extract from, or stdin if omitted",
-						Required:  false,
+						Aliases:   []string{"f", "input", "i"},
+						Usage:     "The car file to extract from. Use a single dash ('-') to read from stdin",
 						TakesFile: true,
 					},
 					&cli.StringFlag{
-						Name:     "path",
-						Aliases:  []string{"p"},
-						Usage:    "The unixfs path to extract",
+						Name:     "output",
+						Aliases:  []string{"o"},
+						Usage:    "The path to write into",
 						Required: false,
 					},
 					&cli.BoolFlag{

cmd/car/extract.go

@@ -22,18 +22,22 @@ var ErrNotDir = fmt.Errorf("not a directory")
 
 // ExtractCar pulls files and directories out of a car
 func ExtractCar(c *cli.Context) error {
+	if !c.IsSet("file") {
+		return fmt.Errorf("a file source must be specified")
+	}
+
 	outputDir, err := os.Getwd()
 	if err != nil {
 		return err
 	}
-	if c.Args().Present() {
-		outputDir = c.Args().First()
+	if c.IsSet("output") {
+		outputDir = c.String("output")
 	}
 
 	var store storage.ReadableStorage
 	var roots []cid.Cid
 
-	if c.String("file") == "" {
+	if c.String("file") == "-" {
 		if f, ok := c.App.Reader.(*os.File); ok {
 			stat, err := f.Stat()
 			if err != nil {
@@ -71,19 +75,28 @@ func ExtractCar(c *cli.Context) error {
 	ls.TrustedStorage = true
 	ls.SetReadStorage(store)
 
-	path, err := pathSegments(c.String("path"))
-	if err != nil {
-		return err
+	paths := c.Args().Slice()
+	if len(paths) == 0 {
+		paths = append(paths, "")
 	}
 
 	var extractedFiles int
-	for _, root := range roots {
-		count, err := lib.ExtractToDir(c.Context, &ls, root, outputDir, path, c.IsSet("verbose"), c.App.ErrWriter)
+
+	for _, p := range paths {
+		path, err := pathSegments(p)
 		if err != nil {
 			return err
 		}
-		extractedFiles += count
+
+		for _, root := range roots {
+			count, err := lib.ExtractToDir(c.Context, &ls, root, outputDir, path, c.IsSet("verbose"), c.App.ErrWriter)
+			if err != nil {
+				return err
+			}
+			extractedFiles += count
+		}
 	}
+
 	if extractedFiles == 0 {
 		return cli.Exit("no files extracted", 1)
 	} else {

cmd/car/testdata/script/create-extract.txt

@@ -1,6 +1,6 @@
 car create --file=out.car foo.txt bar.txt
 mkdir out
-car extract -v -f out.car out
+car extract -v -f out.car -o out
 stderr -count=2 'txt$'
 stderr -count=1 '^extracted 2 file\(s\)$'
 car create --file=out2.car out/foo.txt out/bar.txt

cmd/car/testdata/script/extract.txt

@@ -1,6 +1,6 @@
 # full DAG export, everything in the CAR
 mkdir actual-full
-car extract -f ${INPUTS}/simple-unixfs.car actual-full
+car extract -f ${INPUTS}/simple-unixfs.car -o actual-full
 stderr '^extracted 9 file\(s\)$'
 cmp actual-full/a/1/A.txt expected/a/1/A.txt
 cmp actual-full/a/2/B.txt expected/a/2/B.txt
@@ -15,7 +15,7 @@ cmp actual-full/c/8/H.txt expected/c/8/H.txt
 # full DAG export, everything in the CAR, accepted from stdin
 mkdir actual-stdin
 stdin ${INPUTS}/simple-unixfs.car
-car extract actual-stdin
+car extract -f - -o actual-stdin
 stderr '^extracted 9 file\(s\)$'
 cmp actual-stdin/a/1/A.txt expected/a/1/A.txt
 cmp actual-stdin/a/2/B.txt expected/a/2/B.txt
@@ -29,7 +29,7 @@ cmp actual-stdin/c/8/H.txt expected/c/8/H.txt
 
 # full DAG export, everything in the CAR, but the CAR is missing blocks (incomplete DAG)
 mkdir actual-missing
-car extract -f ${INPUTS}/simple-unixfs-missing-blocks.car actual-missing
+car extract -f ${INPUTS}/simple-unixfs-missing-blocks.car -o actual-missing
 stderr -count=1 'data for entry not found: /b/4 \(skipping\.\.\.\)'
 stderr -count=1 'data for entry not found: /b/5/E.txt \(skipping\.\.\.\)'
 stderr -count=1 'data for entry not found: /b/6 \(skipping\.\.\.\)'
@@ -46,7 +46,7 @@ cmp actual-missing/c/8/H.txt expected/c/8/H.txt
 
 # path-based partial export, everything under the path specified (also without leading / in path)
 mkdir actual-partial
-car extract -f ${INPUTS}/simple-unixfs.car -p b actual-partial
+car extract -f ${INPUTS}/simple-unixfs.car -o actual-partial b
 stderr '^extracted 3 file\(s\)$'
 ! exists actual-partial/a/1/A.txt
 ! exists actual-partial/a/2/B.txt
@@ -60,7 +60,7 @@ cmp actual-partial/b/4/D.txt expected/b/4/D.txt
 
 # path-based single-file export (also with leading /)
 mkdir actual-single
-car extract -f ${INPUTS}/simple-unixfs.car -p /a/2/B.txt actual-single
+car extract -f ${INPUTS}/simple-unixfs.car -o actual-single /a/2/B.txt
 stderr '^extracted 1 file\(s\)$'
 ! exists actual-single/a/1/A.txt
 cmp actual-single/a/2/B.txt expected/a/2/B.txt
@@ -72,18 +72,32 @@ cmp actual-single/a/2/B.txt expected/a/2/B.txt
 ! exists actual-single/c/7/G.txt
 ! exists actual-single/c/8/H.txt
 
+# path-based multiple export
+mkdir actual-multiple
+car extract -f ${INPUTS}/simple-unixfs.car -o actual-multiple /a b/6 /c/7/G.txt
+stderr '^extracted 5 file\(s\)$'
+cmp actual-multiple/a/1/A.txt expected/a/1/A.txt
+cmp actual-multiple/a/2/B.txt expected/a/2/B.txt
+cmp actual-multiple/a/3/C.txt expected/a/3/C.txt
+! exists actual-multiple/b/5/E.txt
+cmp actual-multiple/b/6/F.txt expected/b/6/F.txt
+! exists actual-multiple/b/4/D.txt
+! exists actual-multiple/c/9/I.txt
+cmp actual-multiple/c/7/G.txt expected/c/7/G.txt
+! exists actual-multiple/c/8/H.txt
+
 # extract that doesn't yield any files should error
-! car extract -f ${INPUTS}/simple-unixfs-missing-blocks.car -p b
+! car extract -f ${INPUTS}/simple-unixfs-missing-blocks.car b
 stderr '^no files extracted$'
 
 # car with only one file, nested inside sharded directory, output to stdout
-car extract -f ${INPUTS}/wikipedia-cryptographic-hash-function.car -p wiki/Cryptographic_hash_function -
+car extract -f ${INPUTS}/wikipedia-cryptographic-hash-function.car -o - wiki/Cryptographic_hash_function
 stderr '^extracted 1 file\(s\)$'
 stdout -count=1 '^  <title>Cryptographic hash function</title>$'
 
 # car with only one file, full extract, lots of errors
 mkdir actual-wiki
-car extract -f ${INPUTS}/wikipedia-cryptographic-hash-function.car actual-wiki
+car extract -f ${INPUTS}/wikipedia-cryptographic-hash-function.car -o actual-wiki
 stderr '^extracted 1 file\(s\)$'
 stderr -count=1 '^data for entry not found for 570 unknown sharded entries \(skipped\.\.\.\)$'
 # random sampling of expected skip errors
@@ -110,4 +124,4 @@ c9I
 -- expected/c/7/G.txt --
 c7G
 -- expected/c/8/H.txt --
-c8H
+c8H