git: Extract a zero checksum constant

Previously when a constant zero checksum was required, it was retrieved
from object hash. The checksum hash is completely decoupled from the
object hash and so here we separate these concepts.

4 files changed, 8 insertions, 5 deletions

diff --git a/internal/git/checksum.go b/internal/git/checksum.go
index ce4fb25d0..89f0e8404 100644
--- a/internal/git/checksum.go
+++ b/internal/git/checksum.go
@@ -8,6 +8,9 @@ import (
 	"regexp"
 )
 
+// ZeroChecksum is the hex representation of a checksum with no references added.
+const ZeroChecksum = "0000000000000000000000000000000000000000"
+
 var refsAllowed = regexp.MustCompile(`HEAD|(refs/(heads|tags|keep-around|merge-requests|environments|notes)/)`)
 
 // Checksum is a hash representation of all references in a repository.
@@ -65,7 +68,7 @@ func (c *Checksum) Bytes() []byte {
 // String returns the checksum as a hex encoded string.
 func (c *Checksum) String() string {
 	if c.IsZero() {
-		return ObjectHashSHA1.ZeroOID.String()
+		return ZeroChecksum
 	}
 	return hex.EncodeToString(c.Bytes())
 }
diff --git a/internal/git/checksum_test.go b/internal/git/checksum_test.go
index b70650d3d..dc1f8e8b6 100644
--- a/internal/git/checksum_test.go
+++ b/internal/git/checksum_test.go
@@ -53,7 +53,7 @@ func TestChecksum(t *testing.T) {
 		{
 			desc:         "zero",
 			expectedZero: true,
-			expected:     ObjectHashSHA1.ZeroOID.String(),
+			expected:     ZeroChecksum,
 		},
 		{
 			desc: "single ref",
diff --git a/internal/gitaly/service/repository/calculate_checksum.go b/internal/gitaly/service/repository/calculate_checksum.go
index 6bff6e61d..78d99ccef 100644
--- a/internal/gitaly/service/repository/calculate_checksum.go
+++ b/internal/gitaly/service/repository/calculate_checksum.go
@@ -48,7 +48,7 @@ func (s *server) CalculateChecksum(ctx context.Context, in *gitalypb.CalculateCh
 
 	if err := cmd.Wait(); checksum.IsZero() || err != nil {
 		if s.isValidRepo(ctx, repo) {
-			return &gitalypb.CalculateChecksumResponse{Checksum: git.ObjectHashSHA1.ZeroOID.String()}, nil
+			return &gitalypb.CalculateChecksumResponse{Checksum: git.ZeroChecksum}, nil
 		}
 
 		return nil, status.Errorf(codes.DataLoss, "CalculateChecksum: not a git repository '%s'", repoPath)
diff --git a/internal/gitaly/service/repository/calculate_checksum_test.go b/internal/gitaly/service/repository/calculate_checksum_test.go
index 7924ead17..4ff6b5ec0 100644
--- a/internal/gitaly/service/repository/calculate_checksum_test.go
+++ b/internal/gitaly/service/repository/calculate_checksum_test.go
@@ -51,7 +51,7 @@ func TestEmptyRepositoryCalculateChecksum(t *testing.T) {
 
 	response, err := client.CalculateChecksum(ctx, request)
 	require.NoError(t, err)
-	require.Equal(t, git.ObjectHashSHA1.ZeroOID.String(), response.Checksum)
+	require.Equal(t, git.ZeroChecksum, response.Checksum)
 }
 
 func TestBrokenRepositoryCalculateChecksum(t *testing.T) {
@@ -125,5 +125,5 @@ func TestInvalidRefsCalculateChecksum(t *testing.T) {
 
 	response, err := client.CalculateChecksum(ctx, request)
 	require.NoError(t, err)
-	require.Equal(t, git.ObjectHashSHA1.ZeroOID.String(), response.Checksum)
+	require.Equal(t, git.ZeroChecksum, response.Checksum)
 }