delete stuff from imported dirs when it dissapears

In particular, when we do go vendoring updates and people move their code
around, we wouldn't delete their old code and would get lots of compiler
errors. It's incorrect to leave this code laying around anyway, so let's be
sure to delete it.

Signed-off-by: Tycho Andersen <tycho@tycho.ws>

import.go

@@ -9,7 +9,9 @@ import (
 	"os/exec"
 	"path"
 
+	"github.com/pkg/errors"
 	"github.com/udhos/equalfile"
+	"github.com/vbatts/go-mtree"
 )
 
 func fileCopy(dest string, source string) error {
@@ -92,40 +94,79 @@ func importFile(imp string, cacheDir string) (string, error) {
 		return "", err
 	}
 
-	if e1.IsDir() {
-		binary := "cp"
-		// TODO: use rsync if it is available
-		output, err := exec.Command(binary, "-a", imp, cacheDir).CombinedOutput()
+	if !e1.IsDir() {
+		needsCopy := false
+		dest := path.Join(cacheDir, path.Base(imp))
+		e2, err := os.Stat(dest)
 		if err != nil {
-			return "", fmt.Errorf("%s", string(output))
+			needsCopy = true
+		} else {
+			differ, err := filesDiffer(imp, e1, dest, e2)
+			if err != nil {
+				return "", err
+			}
+
+			needsCopy = differ
 		}
-		return path.Join(cacheDir, path.Base(imp)), nil
+
+		if needsCopy {
+			fmt.Printf("copying %s\n", imp)
+			if err := fileCopy(dest, imp); err != nil {
+				return "", errors.Wrapf(err, "couldn't copy import %s", imp)
+			}
+		} else {
+			fmt.Println("using cached copy of", imp)
+		}
+
+		return dest, nil
+	}
+
+	existing, err := walkImport(cacheDir)
+	if err != nil {
+		return "", errors.Wrapf(err, "failed walking existing import dir")
 	}
 
-	needsCopy := false
 	dest := path.Join(cacheDir, path.Base(imp))
-	e2, err := os.Stat(dest)
+	if err := os.MkdirAll(dest, 0755); err != nil {
+		return "", err
+	}
+
+	toImport, err := walkImport(imp)
 	if err != nil {
-		needsCopy = true
-	} else {
-		differ, err := filesDiffer(imp, e1, dest, e2)
-		if err != nil {
-			return "", err
-		}
+		return "", errors.Wrapf(err, "failed walking dir to import")
+	}
 
-		needsCopy = differ
+	diff, err := mtree.Compare(existing, toImport, mtreeKeywords)
+	if err != nil {
+		return "", err
 	}
 
-	if needsCopy {
-		fmt.Printf("copying %s\n", imp)
-		if err := fileCopy(dest, imp); err != nil {
-			return "", err
+	for _, d := range diff {
+		switch d.Type() {
+		case mtree.Missing:
+			err := os.RemoveAll(path.Join(dest, d.Path()))
+			if err != nil {
+				return "", err
+			}
+		case mtree.Modified:
+			fallthrough
+		case mtree.Extra:
+			err := os.RemoveAll(path.Join(dest, d.Path()))
+			if err != nil && !os.IsNotExist(err) {
+				return "", err
+			}
+
+			output, err := exec.Command("cp", "-a", path.Join(imp, d.Path()), path.Join(dest, d.Path())).CombinedOutput()
+			if err != nil {
+				return "", errors.Wrapf(err, "couldn't copy %s: %s", path.Join(imp, d.Path()), string(output))
+			}
+		case mtree.ErrorDifference:
+			return "", errors.Errorf("failed to diff %s", d.Path())
 		}
-	} else {
-		fmt.Println("using cached copy of", imp)
 	}
 
 	return dest, nil
+
 }
 
 func acquireUrl(c StackerConfig, i string, cache string) (string, error) {

test/caching.bats

@@ -18,7 +18,7 @@ EOF
 
 function teardown() {
     cleanup
-    rm -rf tree1 tree2 link >& /dev/null || true
+    rm -rf tree1 tree2 link foo >& /dev/null || true
 }
 
 @test "import caching" {
@@ -30,3 +30,36 @@ function teardown() {
     umoci unpack --image oci:import-cache dest
     [ "$(sha tree2/foo/foo)" == "$(sha dest/rootfs/foo)" ]
 }
+
+@test "remove from a dir" {
+    cat > stacker.yaml <<EOF
+a:
+    from:
+        type: docker
+        url: docker://centos:latest
+    import:
+        - foo
+    run: |
+        [ -f /stacker/foo/bar ]
+EOF
+
+    mkdir -p foo
+    touch foo/bar
+    stacker build
+    [ "$status" -eq 0 ]
+
+    cat > stacker.yaml <<EOF
+a:
+    from:
+        type: docker
+        url: docker://centos:latest
+    import:
+        - foo
+    run: |
+        [ -f /stacker/foo/baz ]
+EOF
+    rm foo/bar
+    touch foo/baz
+    stacker build
+    [ "$status" -eq 0 ]
+}