Resolve absolute destinations inside the candidate checkout

internal/validation/destination_test.go

@@ -230,3 +230,67 @@ func TestResolveDestinationPreservesParentTraversalOrder(t *testing.T) {
 		t.Fatalf("neighbor changed resolution: %#v -> %#v, %v", before, after, err)
 	}
 }
+
+func TestResolveDestinationMapsAbsolutePathsIntoCandidate(t *testing.T) {
+	repository := newTreeRepository(t)
+	for _, name := range []string{"README.md", "docs/file.md", "nested/file.md", "nested/inner/item.txt"} {
+		writeTreeFile(t, repository, name, []byte("captured\n"))
+	}
+	for name, target := range map[string]string{
+		"absolute-file":      filepath.ToSlash(filepath.Join(repository, "README.md")),
+		"absolute-directory": filepath.ToSlash(filepath.Join(repository, "nested", "inner")),
+		"absolute-outside":   filepath.ToSlash(repository + "-neighbor/README.md"),
+		"docs/link":          "../nested/inner",
+		"absolute-parent":    filepath.ToSlash(repository) + "/docs/link/../file.md",
+	} {
+		if err := os.Symlink(target, filepath.Join(repository, filepath.FromSlash(name))); err != nil {
+			t.Fatal(err)
+		}
+	}
+	gitTree(t, repository, "add", "--all")
+	gitTree(t, repository, "commit", "-m", "capture absolute links")
+	tree, err := ReadCandidateTree(t.Context(), repository, strings.TrimSpace(gitTree(t, repository, "rev-parse", "HEAD")))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Remove(filepath.Join(repository, "README.md")); err != nil {
+		t.Fatal(err)
+	}
+	writeTreeFile(t, repository, "live-only.md", []byte("not committed"))
+	neighbor := repository + "-neighbor"
+	if err := os.MkdirAll(neighbor, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(neighbor, "README.md"), []byte("outside"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		if err := os.RemoveAll(neighbor); err != nil {
+			t.Error(err)
+		}
+	})
+	root := filepath.ToSlash(repository)
+	for _, test := range []struct {
+		destination string
+		kind        DestinationKind
+		resolved    string
+	}{
+		{root + "/README.md", DestinationEntry, "README.md"},
+		{root, DestinationDirectory, "."},
+		{root + "/nested/inner", DestinationDirectory, "nested/inner"},
+		{"absolute-file", DestinationEntry, "README.md"},
+		{"absolute-directory/item.txt", DestinationEntry, "nested/inner/item.txt"},
+		{root + "/docs/link/../file.md", DestinationEntry, "nested/file.md"},
+		{"absolute-parent", DestinationEntry, "nested/file.md"},
+		{root + "/live-only.md", DestinationMissing, "live-only.md"},
+		{root + "-neighbor/README.md", DestinationOutsideCheckout, root + "-neighbor/README.md"},
+		{"absolute-outside", DestinationOutsideCheckout, root + "-neighbor/README.md"},
+	} {
+		t.Run(test.destination, func(t *testing.T) {
+			got, err := tree.ResolveDestination(t.Context(), "README.md", test.destination)
+			if err != nil || got.Kind != test.kind || got.Path != test.resolved {
+				t.Fatalf("resolution = %#v, %v; want %s %q", got, err, test.kind, test.resolved)
+			}
+		})
+	}
+}

internal/validation/tree.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"path"
+	"path/filepath"
 	"strings"
 
 	"gitea.maximumdirect.net/eric/ReleaseKit/internal/git"
@@ -97,16 +98,25 @@ type Destination struct {
 	Path string
 }
 
-// ResolveDestination resolves a repository-relative destination from the
-// source file's directory using only the captured Git tree.
+// ResolveDestination resolves local destinations using the captured Git tree.
+// Relative destinations start at the source directory; absolute destinations
+// within the repository directory map back to committed paths.
 func (tree *CandidateTree) ResolveDestination(ctx context.Context, sourcePath, destination string) (Destination, error) {
 	if err := ctx.Err(); err != nil {
 		return Destination{}, err
 	}
-	if strings.HasPrefix(destination, "/") {
-		return Destination{Kind: DestinationOutsideCheckout, Path: path.Clean(destination)}, nil
+	directory := path.Dir(sourcePath)
+	if path.IsAbs(destination) {
+		relative, inside, err := tree.relativeAbsoluteDestination(destination)
+		if err != nil {
+			return Destination{}, err
+		}
+		if !inside {
+			return Destination{Kind: DestinationOutsideCheckout, Path: destination}, nil
+		}
+		directory, destination = ".", relative
 	}
-	return tree.resolveDestination(ctx, path.Dir(sourcePath), strings.Split(destination, "/"), make(map[string]bool))
+	return tree.resolveDestination(ctx, directory, strings.Split(destination, "/"), make(map[string]bool))
 }
 
 func (tree *CandidateTree) resolveDestination(ctx context.Context, directory string, components []string, active map[string]bool) (Destination, error) {
@@ -146,11 +156,19 @@ func (tree *CandidateTree) resolveDestination(ctx context.Context, directory str
 				return Destination{}, fmt.Errorf("read committed symlink %q: %w", partial, err)
 			}
 			target := string(linkText)
-			if strings.HasPrefix(target, "/") {
-				return Destination{Kind: DestinationOutsideCheckout, Path: unresolvedPath(target, remaining)}, nil
+			targetDirectory := directory
+			if path.IsAbs(target) {
+				relative, inside, err := tree.relativeAbsoluteDestination(target)
+				if err != nil {
+					return Destination{}, err
+				}
+				if !inside {
+					return Destination{Kind: DestinationOutsideCheckout, Path: unresolvedPath(target, remaining)}, nil
+				}
+				targetDirectory, target = ".", relative
 			}
 			active[partial] = true
-			destination, err := tree.resolveDestination(ctx, directory, strings.Split(target, "/"), active)
+			destination, err := tree.resolveDestination(ctx, targetDirectory, strings.Split(target, "/"), active)
 			delete(active, partial)
 			if err != nil || len(remaining) == 0 {
 				return destination, err
@@ -174,6 +192,20 @@ func (tree *CandidateTree) resolveDestination(ctx context.Context, directory str
 	return Destination{Kind: DestinationDirectory, Path: directory}, nil
 }
 
+func (tree *CandidateTree) relativeAbsoluteDestination(destination string) (string, bool, error) {
+	root, err := filepath.Abs(tree.repositoryDir)
+	if err != nil {
+		return "", false, fmt.Errorf("resolve candidate repository directory: %w", err)
+	}
+	root = filepath.ToSlash(root)
+	if destination == root {
+		return ".", true, nil
+	}
+	// Preserve the suffix for component traversal, including symlinks before '..'.
+	relative, inside := strings.CutPrefix(destination, strings.TrimSuffix(root, "/")+"/")
+	return relative, inside, nil
+}
+
 // unresolvedPath preserves components that could not be traversed. Cleaning
 // them would hide missing entries, non-directories, or checkout boundaries.
 func unresolvedPath(base string, remaining []string) string {