fetch: More Git fixes

Author: ianprime0509

lib/std/Io/Writer.zig

@@ -2418,7 +2418,7 @@ pub fn Hashing(comptime Hasher: type) type {
                 n += slice.len;
             }
             for (0..splat) |_| hasher.update(data[data.len - 1]);
-            return n + splat;
+            return n + splat * data[data.len - 1].len;
         }
     };
 }

src/Package/Fetch/git.zig

@@ -1500,13 +1500,11 @@ fn readObjectRaw(allocator: Allocator, reader: *std.Io.Reader, size: u64) ![]u8
     return aw.toOwnedSlice();
 }
 
-/// Expands delta data from `delta_reader` to `writer`. `base_object` must
-/// support `reader` and `seekTo` (such as a `std.io.FixedBufferStream`).
+/// Expands delta data from `delta_reader` to `writer`.
 ///
 /// The format of the delta data is documented in
 /// [pack-format](https://git-scm.com/docs/pack-format).
 fn expandDelta(base_object: []const u8, delta_reader: *std.Io.Reader, writer: *std.Io.Writer) !void {
-    var base_offset: u32 = 0;
     while (true) {
         const inst: packed struct { value: u7, copy: bool } = @bitCast(delta_reader.takeByte() catch |e| switch (e) {
             error.EndOfStream => return,
@@ -1528,7 +1526,7 @@ fn expandDelta(base_object: []const u8, delta_reader: *std.Io.Reader, writer: *s
                 .offset3 = if (available.offset3) try delta_reader.takeByte() else 0,
                 .offset4 = if (available.offset4) try delta_reader.takeByte() else 0,
             };
-            base_offset = @bitCast(offset_parts);
+            const base_offset: u32 = @bitCast(offset_parts);
             const size_parts: packed struct { size1: u8, size2: u8, size3: u8 } = .{
                 .size1 = if (available.size1) try delta_reader.takeByte() else 0,
                 .size2 = if (available.size2) try delta_reader.takeByte() else 0,
@@ -1537,7 +1535,6 @@ fn expandDelta(base_object: []const u8, delta_reader: *std.Io.Reader, writer: *s
             var size: u24 = @bitCast(size_parts);
             if (size == 0) size = 0x10000;
             try writer.writeAll(base_object[base_offset..][0..size]);
-            base_offset += size;
         } else if (inst.value != 0) {
             try delta_reader.streamExact(writer, inst.value);
         } else {
@@ -1582,13 +1579,15 @@ fn runRepositoryTest(comptime format: Oid.Format, head_commit: []const u8) !void
     // (all files in the test repo are known to be smaller than this)
     const max_file_size = 8192;
 
-    const index_file_data = try git_dir.dir.readFileAlloc(testing.allocator, "testrepo.idx", max_file_size);
-    defer testing.allocator.free(index_file_data);
-    // testrepo.idx is generated by Git. The index created by this file should
-    // match it exactly. Running `git verify-pack -v testrepo.pack` can verify
-    // this.
-    const testrepo_idx = @embedFile("git/testdata/testrepo-" ++ @tagName(format) ++ ".idx");
-    try testing.expectEqualSlices(u8, testrepo_idx, index_file_data);
+    if (!skip_checksums) {
+        const index_file_data = try git_dir.dir.readFileAlloc(testing.allocator, "testrepo.idx", max_file_size);
+        defer testing.allocator.free(index_file_data);
+        // testrepo.idx is generated by Git. The index created by this file should
+        // match it exactly. Running `git verify-pack -v testrepo.pack` can verify
+        // this.
+        const testrepo_idx = @embedFile("git/testdata/testrepo-" ++ @tagName(format) ++ ".idx");
+        try testing.expectEqualSlices(u8, testrepo_idx, index_file_data);
+    }
 
     var index_file_reader = index_file.reader(&index_file_buffer);
     var repository: Repository = undefined;
@@ -1669,12 +1668,10 @@ fn runRepositoryTest(comptime format: Oid.Format, head_commit: []const u8) !void
 const skip_checksums = true;
 
 test "SHA-1 packfile indexing and checkout" {
-    if (skip_checksums) return error.SkipZigTest;
     try runRepositoryTest(.sha1, "dd582c0720819ab7130b103635bd7271b9fd4feb");
 }
 
 test "SHA-256 packfile indexing and checkout" {
-    if (skip_checksums) return error.SkipZigTest;
     try runRepositoryTest(.sha256, "7f444a92bd4572ee4a28b2c63059924a9ca1829138553ef3e7c41ee159afae7a");
 }