Refactor context RefName and RepoAssignment (#33226)

The `ctx.Repo.RefName` was used to be a "short name", it causes a lot of
ambiguity.

This PR does some refactoring and use `RefFullName` to replace the
legacy `RefName`, and simplify RepoAssignment

modules/git/repo_archive_test.go

@@ -0,0 +1,32 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package git
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestArchiveType(t *testing.T) {
+	name, archiveType := SplitArchiveNameType("test.tar.gz")
+	assert.Equal(t, "test", name)
+	assert.Equal(t, "tar.gz", archiveType.String())
+
+	name, archiveType = SplitArchiveNameType("a/b/test.zip")
+	assert.Equal(t, "a/b/test", name)
+	assert.Equal(t, "zip", archiveType.String())
+
+	name, archiveType = SplitArchiveNameType("1234.bundle")
+	assert.Equal(t, "1234", name)
+	assert.Equal(t, "bundle", archiveType.String())
+
+	name, archiveType = SplitArchiveNameType("test")
+	assert.Equal(t, "test", name)
+	assert.Equal(t, "unknown", archiveType.String())
+
+	name, archiveType = SplitArchiveNameType("test.xz")
+	assert.Equal(t, "test.xz", name)
+	assert.Equal(t, "unknown", archiveType.String())
+}