add a discrete clone method to scopes (#1626)

## Description

Adds a method to all scopes that produces a
discrete clone of the original scope.  The result is a shallow clone of the scope, thus retaining all
original values, but is made discrete by replacing the resource owner target with a specific value.

## Type of change

- [x] 🌻 Feature

## Issue(s)

* #1621

## Test Plan

- [x] ⚡ Unit test

src/pkg/selectors/exchange.go

@@ -686,6 +686,12 @@ func (s ExchangeScope) setDefaults() {
 	}
 }
 
+// DiscreteCopy makes a shallow clone of the scope, then replaces the clone's
+// user comparison with only the provided user.
+func (s ExchangeScope) DiscreteCopy(user string) ExchangeScope {
+	return discreteCopy(s, user)
+}
+
 // ---------------------------------------------------------------------------
 // Backup Details Filtering
 // ---------------------------------------------------------------------------

src/pkg/selectors/onedrive.go

@@ -459,6 +459,29 @@ func (s OneDriveScope) setDefaults() {
 	}
 }
 
+// DiscreteCopy makes a clone of the scope, then replaces the clone's user comparison
+// with only the provided user.
+func (s OneDriveScope) DiscreteCopy(user string) OneDriveScope {
+	return discreteCopy(s, user)
+}
+
+// ---------------------------------------------------------------------------
+// Backup Details Filtering
+// ---------------------------------------------------------------------------
+
+// Reduce filters the entries in a details struct to only those that match the
+// inclusions, filters, and exclusions in the selector.
+func (s oneDrive) Reduce(ctx context.Context, deets *details.Details) *details.Details {
+	return reduce[OneDriveScope](
+		ctx,
+		deets,
+		s.Selector,
+		map[path.CategoryType]oneDriveCategory{
+			path.FilesCategory: OneDriveItem,
+		},
+	)
+}
+
 // matchesInfo handles the standard behavior when comparing a scope and an oneDriveInfo
 // returns true if the scope and info match for the provided category.
 func (s OneDriveScope) matchesInfo(dii details.ItemInfo) bool {
@@ -480,20 +503,3 @@ func (s OneDriveScope) matchesInfo(dii details.ItemInfo) bool {
 
 	return s.Matches(filterCat, i)
 }
-
-// ---------------------------------------------------------------------------
-// Backup Details Filtering
-// ---------------------------------------------------------------------------
-
-// Reduce filters the entries in a details struct to only those that match the
-// inclusions, filters, and exclusions in the selector.
-func (s oneDrive) Reduce(ctx context.Context, deets *details.Details) *details.Details {
-	return reduce[OneDriveScope](
-		ctx,
-		deets,
-		s.Selector,
-		map[path.CategoryType]oneDriveCategory{
-			path.FilesCategory: OneDriveItem,
-		},
-	)
-}

src/pkg/selectors/scopes.go

@@ -243,6 +243,21 @@ func set[T scopeT](s T, cat categorizer, v []string, opts ...option) T {
 	return s
 }
 
+// discreteCopy makes a shallow clone of the scocpe, and sets the resource
+// owner filter target in the clone to the provided string.
+func discreteCopy[T scopeT](s T, resourceOwner string) T {
+	clone := T{}
+
+	for k, v := range s {
+		clone[k] = v
+	}
+
+	return set(
+		clone,
+		clone.categorizer().rootCat(),
+		[]string{resourceOwner})
+}
+
 // returns true if the category is included in the scope's category type,
 // and the value is set to None().
 func isNoneTarget[T scopeT, C categoryT](s T, cat C) bool {

src/pkg/selectors/scopes_test.go

@@ -513,3 +513,20 @@ func (suite *SelectorScopesSuite) TestScopeConfig() {
 		})
 	}
 }
+
+func (suite *SelectorScopesSuite) TestDiscreteCopy() {
+	var (
+		t     = suite.T()
+		orig  = stubScope(AnyTgt)
+		clone = discreteCopy(orig, "fnords")
+	)
+
+	for k, v := range orig {
+		if k != rootCatStub.String() {
+			assert.Equal(t, v.Target, clone[k].Target)
+		} else {
+			assert.Equal(t, AnyTgt, v.Target)
+			assert.Equal(t, "fnords", clone[k].Target)
+		}
+	}
+}

src/pkg/selectors/sharepoint.go

@@ -407,6 +407,30 @@ func (s SharePointScope) setDefaults() {
 	}
 }
 
+// DiscreteCopy makes a shallow clone of the scope, then replaces the clone's
+// site comparison with only the provided site.
+func (s SharePointScope) DiscreteCopy(site string) SharePointScope {
+	return discreteCopy(s, site)
+}
+
+// ---------------------------------------------------------------------------
+// Backup Details Filtering
+// ---------------------------------------------------------------------------
+
+// Reduce filters the entries in a details struct to only those that match the
+// inclusions, filters, and exclusions in the selector.
+func (s sharePoint) Reduce(ctx context.Context, deets *details.Details) *details.Details {
+	return reduce[SharePointScope](
+		ctx,
+		deets,
+		s.Selector,
+		map[path.CategoryType]sharePointCategory{
+			path.LibrariesCategory: SharePointLibraryItem,
+			// TODO: list category type
+		},
+	)
+}
+
 // matchesInfo handles the standard behavior when comparing a scope and an sharePointInfo
 // returns true if the scope and info match for the provided category.
 func (s SharePointScope) matchesInfo(dii details.ItemInfo) bool {
@@ -428,21 +452,3 @@ func (s SharePointScope) matchesInfo(dii details.ItemInfo) bool {
 
 	return s.Matches(filterCat, i)
 }
-
-// ---------------------------------------------------------------------------
-// Backup Details Filtering
-// ---------------------------------------------------------------------------
-
-// Reduce filters the entries in a details struct to only those that match the
-// inclusions, filters, and exclusions in the selector.
-func (s sharePoint) Reduce(ctx context.Context, deets *details.Details) *details.Details {
-	return reduce[SharePointScope](
-		ctx,
-		deets,
-		s.Selector,
-		map[path.CategoryType]sharePointCategory{
-			path.LibrariesCategory: SharePointLibraryItem,
-			// TODO: list category type
-		},
-	)
-}