Merge pull request #38 from go-git/feature/difftree-renames

plumbing: detect renames by hash and similar content in diff tree

1 files changed, 64 insertions, 3 deletions

diff --git a/plumbing/object/difftree.go b/plumbing/object/difftree.go
index 72411a5..7c22227 100644
--- a/plumbing/object/difftree.go
+++ b/plumbing/object/difftree.go
@@ -10,14 +10,62 @@ import (
 
 // DiffTree compares the content and mode of the blobs found via two
 // tree objects.
+// DiffTree does not perform rename detection, use DiffTreeWithOptions
+// instead to detect renames.
 func DiffTree(a, b *Tree) (Changes, error) {
 	return DiffTreeContext(context.Background(), a, b)
 }
 
-// DiffTree compares the content and mode of the blobs found via two
+// DiffTreeContext compares the content and mode of the blobs found via two
 // tree objects. Provided context must be non-nil.
-// An error will be return if context expires
+// An error will be returned if context expires.
 func DiffTreeContext(ctx context.Context, a, b *Tree) (Changes, error) {
+	return DiffTreeWithOptions(ctx, a, b, nil)
+}
+
+// DiffTreeOptions are the configurable options when performing a diff tree.
+type DiffTreeOptions struct {
+	// DetectRenames is whether the diff tree will use rename detection.
+	DetectRenames bool
+	// RenameScore is the threshold to of similarity between files to consider
+	// that a pair of delete and insert are a rename. The number must be
+	// exactly between 0 and 100.
+	RenameScore uint
+	// RenameLimit is the maximum amount of files that can be compared when
+	// detecting renames. The number of comparisons that have to be performed
+	// is equal to the number of deleted files * the number of added files.
+	// That means, that if 100 files were deleted and 50 files were added, 5000
+	// file comparisons may be needed. So, if the rename limit is 50, the number
+	// of both deleted and added needs to be equal or less than 50.
+	// A value of 0 means no limit.
+	RenameLimit uint
+	// OnlyExactRenames performs only detection of exact renames and will not perform
+	// any detection of renames based on file similarity.
+	OnlyExactRenames bool
+}
+
+// DefaultDiffTreeOptions are the default and recommended options for the
+// diff tree.
+var DefaultDiffTreeOptions = &DiffTreeOptions{
+	DetectRenames:    true,
+	RenameScore:      60,
+	RenameLimit:      0,
+	OnlyExactRenames: false,
+}
+
+// DiffTreeWithOptions compares the content and mode of the blobs found
+// via two tree objects with the given options. The provided context
+// must be non-nil.
+// If no options are passed, no rename detection will be performed. The
+// recommended options are DefaultDiffTreeOptions.
+// An error will be returned if the context expires.
+// This function will be deprecated and removed in v6 so the default
+// behaviour of DiffTree is to detect renames.
+func DiffTreeWithOptions(
+	ctx context.Context,
+	a, b *Tree,
+	opts *DiffTreeOptions,
+) (Changes, error) {
 	from := NewTreeRootNode(a)
 	to := NewTreeRootNode(b)
 
@@ -33,5 +81,18 @@ func DiffTreeContext(ctx context.Context, a, b *Tree) (Changes, error) {
 		return nil, err
 	}
 
-	return newChanges(merkletrieChanges)
+	changes, err := newChanges(merkletrieChanges)
+	if err != nil {
+		return nil, err
+	}
+
+	if opts == nil {
+		opts = new(DiffTreeOptions)
+	}
+
+	if opts.DetectRenames {
+		return DetectRenames(changes, opts)
+	}
+
+	return changes, nil
 }