From 89cce891887e85b7b1bc43958f24c558d637143f Mon Sep 17 00:00:00 2001
From: Nikolay Edigaryev <edigaryev@gmail.com>
Date: Fri, 12 Apr 2024 02:01:46 +0400
Subject: plumbing: protocol/packp, client-side filter capability support
 (#1000)

* plumbing: protocol/packp, client-side filter capability support
---
 plumbing/protocol/packp/filter.go            | 76 ++++++++++++++++++++++++++++
 plumbing/protocol/packp/filter_test.go       | 58 +++++++++++++++++++++
 plumbing/protocol/packp/ulreq.go             |  1 +
 plumbing/protocol/packp/ulreq_encode.go      | 11 ++++
 plumbing/protocol/packp/ulreq_encode_test.go | 14 +++++
 5 files changed, 160 insertions(+)
 create mode 100644 plumbing/protocol/packp/filter.go
 create mode 100644 plumbing/protocol/packp/filter_test.go

diff --git a/plumbing/protocol/packp/filter.go b/plumbing/protocol/packp/filter.go
new file mode 100644
index 0000000..145fc71
--- /dev/null
+++ b/plumbing/protocol/packp/filter.go
@@ -0,0 +1,76 @@
+package packp
+
+import (
+	"errors"
+	"fmt"
+	"github.com/go-git/go-git/v5/plumbing"
+	"net/url"
+	"strings"
+)
+
+var ErrUnsupportedObjectFilterType = errors.New("unsupported object filter type")
+
+// Filter values enable the partial clone capability which causes
+// the server to omit objects that match the filter.
+//
+// See [Git's documentation] for more details.
+//
+// [Git's documentation]: https://github.com/git/git/blob/e02ecfcc534e2021aae29077a958dd11c3897e4c/Documentation/rev-list-options.txt#L948
+type Filter string
+
+type BlobLimitPrefix string
+
+const (
+	BlobLimitPrefixNone BlobLimitPrefix = ""
+	BlobLimitPrefixKibi BlobLimitPrefix = "k"
+	BlobLimitPrefixMebi BlobLimitPrefix = "m"
+	BlobLimitPrefixGibi BlobLimitPrefix = "g"
+)
+
+// FilterBlobNone omits all blobs.
+func FilterBlobNone() Filter {
+	return "blob:none"
+}
+
+// FilterBlobLimit omits blobs of size at least n bytes (when prefix is
+// BlobLimitPrefixNone), n kibibytes (when prefix is BlobLimitPrefixKibi),
+// n mebibytes (when prefix is BlobLimitPrefixMebi) or n gibibytes (when
+// prefix is BlobLimitPrefixGibi). n can be zero, in which case all blobs
+// will be omitted.
+func FilterBlobLimit(n uint64, prefix BlobLimitPrefix) Filter {
+	return Filter(fmt.Sprintf("blob:limit=%d%s", n, prefix))
+}
+
+// FilterTreeDepth omits all blobs and trees whose depth from the root tree
+// is larger or equal to depth.
+func FilterTreeDepth(depth uint64) Filter {
+	return Filter(fmt.Sprintf("tree:%d", depth))
+}
+
+// FilterObjectType omits all objects which are not of the requested type t.
+// Supported types are TagObject, CommitObject, TreeObject and BlobObject.
+func FilterObjectType(t plumbing.ObjectType) (Filter, error) {
+	switch t {
+	case plumbing.TagObject:
+		fallthrough
+	case plumbing.CommitObject:
+		fallthrough
+	case plumbing.TreeObject:
+		fallthrough
+	case plumbing.BlobObject:
+		return Filter(fmt.Sprintf("object:type=%s", t.String())), nil
+	default:
+		return "", fmt.Errorf("%w: %s", ErrUnsupportedObjectFilterType, t.String())
+	}
+}
+
+// FilterCombine combines multiple Filter values together.
+func FilterCombine(filters ...Filter) Filter {
+	var escapedFilters []string
+
+	for _, filter := range filters {
+		escapedFilters = append(escapedFilters, url.QueryEscape(string(filter)))
+	}
+
+	return Filter(fmt.Sprintf("combine:%s", strings.Join(escapedFilters, "+")))
+}
diff --git a/plumbing/protocol/packp/filter_test.go b/plumbing/protocol/packp/filter_test.go
new file mode 100644
index 0000000..266670f
--- /dev/null
+++ b/plumbing/protocol/packp/filter_test.go
@@ -0,0 +1,58 @@
+package packp
+
+import (
+	"github.com/go-git/go-git/v5/plumbing"
+	"github.com/stretchr/testify/require"
+	"testing"
+)
+
+func TestFilterBlobNone(t *testing.T) {
+	require.EqualValues(t, "blob:none", FilterBlobNone())
+}
+
+func TestFilterBlobLimit(t *testing.T) {
+	require.EqualValues(t, "blob:limit=0", FilterBlobLimit(0, BlobLimitPrefixNone))
+	require.EqualValues(t, "blob:limit=1000", FilterBlobLimit(1000, BlobLimitPrefixNone))
+	require.EqualValues(t, "blob:limit=4k", FilterBlobLimit(4, BlobLimitPrefixKibi))
+	require.EqualValues(t, "blob:limit=4m", FilterBlobLimit(4, BlobLimitPrefixMebi))
+	require.EqualValues(t, "blob:limit=4g", FilterBlobLimit(4, BlobLimitPrefixGibi))
+}
+
+func TestFilterTreeDepth(t *testing.T) {
+	require.EqualValues(t, "tree:0", FilterTreeDepth(0))
+	require.EqualValues(t, "tree:1", FilterTreeDepth(1))
+	require.EqualValues(t, "tree:2", FilterTreeDepth(2))
+}
+
+func TestFilterObjectType(t *testing.T) {
+	filter, err := FilterObjectType(plumbing.TagObject)
+	require.NoError(t, err)
+	require.EqualValues(t, "object:type=tag", filter)
+
+	filter, err = FilterObjectType(plumbing.CommitObject)
+	require.NoError(t, err)
+	require.EqualValues(t, "object:type=commit", filter)
+
+	filter, err = FilterObjectType(plumbing.TreeObject)
+	require.NoError(t, err)
+	require.EqualValues(t, "object:type=tree", filter)
+
+	filter, err = FilterObjectType(plumbing.BlobObject)
+	require.NoError(t, err)
+	require.EqualValues(t, "object:type=blob", filter)
+
+	_, err = FilterObjectType(plumbing.InvalidObject)
+	require.Error(t, err)
+
+	_, err = FilterObjectType(plumbing.OFSDeltaObject)
+	require.Error(t, err)
+}
+
+func TestFilterCombine(t *testing.T) {
+	require.EqualValues(t, "combine:tree%3A2+blob%3Anone",
+		FilterCombine(
+			FilterTreeDepth(2),
+			FilterBlobNone(),
+		),
+	)
+}
diff --git a/plumbing/protocol/packp/ulreq.go b/plumbing/protocol/packp/ulreq.go
index 344f8c7..ef4e08a 100644
--- a/plumbing/protocol/packp/ulreq.go
+++ b/plumbing/protocol/packp/ulreq.go
@@ -17,6 +17,7 @@ type UploadRequest struct {
 	Wants        []plumbing.Hash
 	Shallows     []plumbing.Hash
 	Depth        Depth
+	Filter       Filter
 }
 
 // Depth values stores the desired depth of the requested packfile: see
diff --git a/plumbing/protocol/packp/ulreq_encode.go b/plumbing/protocol/packp/ulreq_encode.go
index c451e23..8b19c0f 100644
--- a/plumbing/protocol/packp/ulreq_encode.go
+++ b/plumbing/protocol/packp/ulreq_encode.go
@@ -132,6 +132,17 @@ func (e *ulReqEncoder) encodeDepth() stateFn {
 		return nil
 	}
 
+	return e.encodeFilter
+}
+
+func (e *ulReqEncoder) encodeFilter() stateFn {
+	if filter := e.data.Filter; filter != "" {
+		if err := e.pe.Encodef("filter %s\n", filter); err != nil {
+			e.err = fmt.Errorf("encoding filter %s: %s", filter, err)
+			return nil
+		}
+	}
+
 	return e.encodeFlush
 }
 
diff --git a/plumbing/protocol/packp/ulreq_encode_test.go b/plumbing/protocol/packp/ulreq_encode_test.go
index ba6df1a..247de27 100644
--- a/plumbing/protocol/packp/ulreq_encode_test.go
+++ b/plumbing/protocol/packp/ulreq_encode_test.go
@@ -273,6 +273,20 @@ func (s *UlReqEncodeSuite) TestDepthReference(c *C) {
 	testUlReqEncode(c, ur, expected)
 }
 
+func (s *UlReqEncodeSuite) TestFilter(c *C) {
+	ur := NewUploadRequest()
+	ur.Wants = append(ur.Wants, plumbing.NewHash("1111111111111111111111111111111111111111"))
+	ur.Filter = FilterTreeDepth(0)
+
+	expected := []string{
+		"want 1111111111111111111111111111111111111111\n",
+		"filter tree:0\n",
+		pktline.FlushString,
+	}
+
+	testUlReqEncode(c, ur, expected)
+}
+
 func (s *UlReqEncodeSuite) TestAll(c *C) {
 	ur := NewUploadRequest()
 	ur.Wants = append(ur.Wants,
-- 
cgit