Add DiffBlobs

This lets you diff two arbitrary blobs with arbitrary names.

diff.go

@@ -5,6 +5,7 @@ package git
 
 extern int _go_git_diff_foreach(git_diff *diff, int eachFile, int eachHunk, int eachLine, void *payload);
 extern void _go_git_setup_diff_notify_callbacks(git_diff_options* opts);
+extern int _go_git_diff_blobs(git_blob *old, const char *old_path, git_blob *new, const char *new_path, git_diff_options *opts, int eachFile, int eachHunk, int eachLine, void *payload);
 */
 import "C"
 import (
@@ -670,3 +671,50 @@ func (v *Repository) DiffIndexToWorkdir(index *Index, opts *DiffOptions) (*Diff,
 	}
 	return newDiffFromC(diffPtr), nil
 }
+
+// DiffBlobs performs a diff between two arbitrary blobs. You can pass
+// whatever file names you'd like for them to appear as in the diff.
+func DiffBlobs(oldBlob *Blob, oldAsPath string, newBlob *Blob, newAsPath string, opts *DiffOptions, fileCallback DiffForEachFileCallback, detail DiffDetail) error {
+	data := &diffForEachData{
+		FileCallback: fileCallback,
+	}
+
+	intHunks := C.int(0)
+	if detail >= DiffDetailHunks {
+		intHunks = C.int(1)
+	}
+
+	intLines := C.int(0)
+	if detail >= DiffDetailLines {
+		intLines = C.int(1)
+	}
+
+	handle := pointerHandles.Track(data)
+	defer pointerHandles.Untrack(handle)
+
+	var oldBlobPtr, newBlobPtr *C.git_blob
+	if oldBlob != nil {
+		oldBlobPtr = oldBlob.cast_ptr
+	}
+	if newBlob != nil {
+		newBlobPtr = newBlob.cast_ptr
+	}
+
+	oldBlobPath := C.CString(oldAsPath)
+	defer C.free(unsafe.Pointer(oldBlobPath))
+	newBlobPath := C.CString(newAsPath)
+	defer C.free(unsafe.Pointer(newBlobPath))
+
+	copts, _ := diffOptionsToC(opts)
+	defer freeDiffOptions(copts)
+
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	ecode := C._go_git_diff_blobs(oldBlobPtr, oldBlobPath, newBlobPtr, newBlobPath, copts, 1, intHunks, intLines, handle)
+	if ecode < 0 {
+		return MakeGitError(ecode)
+	}
+
+	return nil
+}

diff_test.go

@@ -187,3 +187,50 @@ func createTestTrees(t *testing.T, repo *Repository) (originalTree *Tree, newTre
 
 	return originalTree, newTree
 }
+
+func TestDiffBlobs(t *testing.T) {
+	repo := createTestRepo(t)
+	defer cleanupTestRepo(t, repo)
+
+	odb, err := repo.Odb()
+	checkFatal(t, err)
+
+	id1, err := odb.Write([]byte("hello\nhello\n"), ObjectBlob)
+	checkFatal(t, err)
+
+	id2, err := odb.Write([]byte("hallo\nhallo\n"), ObjectBlob)
+	checkFatal(t, err)
+
+	blob1, err := repo.LookupBlob(id1)
+	checkFatal(t, err)
+
+	blob2, err := repo.LookupBlob(id2)
+	checkFatal(t, err)
+
+	var files, hunks, lines int
+	err = DiffBlobs(blob1, "hi", blob2, "hi", nil,
+		func(delta DiffDelta, progress float64) (DiffForEachHunkCallback, error) {
+			files++
+			return func(hunk DiffHunk) (DiffForEachLineCallback, error) {
+				hunks++
+				return func(line DiffLine) error {
+					lines++
+					return nil
+				}, nil
+			}, nil
+		},
+		DiffDetailLines)
+
+	if files != 1 {
+		t.Fatal("Bad number of files iterated")
+	}
+
+	if hunks != 1 {
+		t.Fatal("Bad number of hunks iterated")
+	}
+
+	// two removals, two additions
+	if lines != 4 {
+		t.Fatalf("Bad number of lines iterated")
+	}
+}

wrapper.c

@@ -62,6 +62,27 @@ int _go_git_diff_foreach(git_diff *diff, int eachFile, int eachHunk, int eachLin
 	return git_diff_foreach(diff, fcb, hcb, lcb, payload);
 }
 
+int _go_git_diff_blobs(git_blob *old, const char *old_path, git_blob *new, const char *new_path, git_diff_options *opts, int eachFile, int eachHunk, int eachLine, void *payload)
+{
+	git_diff_file_cb fcb = NULL;
+	git_diff_hunk_cb hcb = NULL;
+	git_diff_line_cb lcb = NULL;
+
+	if (eachFile) {
+		fcb = (git_diff_file_cb)&diffForEachFileCb;
+	}
+
+	if (eachHunk) {
+		hcb = (git_diff_hunk_cb)&diffForEachHunkCb;
+	}
+
+	if (eachLine) {
+		lcb = (git_diff_line_cb)&diffForEachLineCb;
+	}
+
+	return git_diff_blobs(old, old_path, new, new_path, opts, fcb, hcb, lcb, payload);
+}
+
 void _go_git_setup_diff_notify_callbacks(git_diff_options *opts) {
 	opts->notify_cb = (git_diff_notify_cb)diffNotifyCb;
 }