git: Implement version check for git-update-ref(1) status flushing

In the updateref package, we'll want to conditionally wait for status
reports after doing transactional status transitions. This logic depends
on whether git-update-ref(1) correctly flushes status updates to its
stdout though, which is only supported starting either with Git v2.34 or
with our backported patch in Git v2.33.0.gl3.

Provide a function which determines support for correct flushing
semantics via a version check.

2 files changed, 36 insertions, 0 deletions

diff --git a/internal/git/version.go b/internal/git/version.go
index 0fdbc091e..dddf152ee 100644
--- a/internal/git/version.go
+++ b/internal/git/version.go
@@ -104,6 +104,23 @@ func (v Version) SupportsObjectTypeFilter() bool {
 	return !v.LessThan(Version{major: 2, minor: 32, patch: 0})
 }
 
+// FlushesUpdaterefStatus determines whether the given Git version properly flushes status messages
+// in git-update-ref(1).
+func (v Version) FlushesUpdaterefStatus() bool {
+	// We need to be a bit more careful here given that this comes in via a custom patch. The
+	// fix will be released as part of v2.34, so it's either in v2.33 with at least patch level
+	// 3, or it's greater than or equal to v2.34.
+	switch {
+	case v.major == 2 && v.minor == 33 && v.gl >= 3:
+		return true
+	case v.major == 2 && v.minor >= 34:
+		return true
+	case v.major >= 3:
+		return true
+	}
+	return false
+}
+
 // LessThan determines whether the version is older than another version.
 func (v Version) LessThan(other Version) bool {
 	switch {
diff --git a/internal/git/version_test.go b/internal/git/version_test.go
index a7a31c392..a452c0f50 100644
--- a/internal/git/version_test.go
+++ b/internal/git/version_test.go
@@ -247,6 +247,25 @@ func TestVersion_SupportsObjectTypeFilter(t *testing.T) {
 		version string
 		expect  bool
 	}{
+		{"2.32.0.gl3", false},
+		{"2.33.0.gl3", true},
+		{"2.33.1.gl3", true},
+		{"2.34.0", true},
+		{"3.0.0", true},
+	} {
+		t.Run(tc.version, func(t *testing.T) {
+			version, err := parseVersion(tc.version)
+			require.NoError(t, err)
+			require.Equal(t, tc.expect, version.FlushesUpdaterefStatus())
+		})
+	}
+}
+
+func TestVersion_FlushesUpdaterefStatus(t *testing.T) {
+	for _, tc := range []struct {
+		version string
+		expect  bool
+	}{
 		{"2.31.0", false},
 		{"2.31.0-rc0", false},
 		{"2.31.1", false},