Fix incorrect vendored detections (#36508)

Fixes: https://github.com/go-gitea/gitea/issues/22618

`go-enry`'s `IsVendor` function marks git paths (`.gitignore`,
`.gitattributes`, `.gitmodules`), github/gitea paths (`.github/`,
`.gitea/`) as "vendored" for GitHub Linguist language statistics. This
causes these files to incorrectly display the "Vendored" tag in diff
views.

Override `go-enry`'s detection for these specific cases while preserving
its behavior for actual vendor directories.

---------

Signed-off-by: silverwind <me@silverwind.io>
Signed-off-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: silverwind <115237+silverwind@users.noreply.github.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/analyze/vendor_test.go

@@ -14,6 +14,7 @@ func TestIsVendor(t *testing.T) {
 		path string
 		want bool
 	}{
+		// Original go-enry test cases
 		{"cache/", true},
 		{"random/cache/", true},
 		{"cache", false},
@@ -34,6 +35,14 @@ func TestIsVendor(t *testing.T) {
 		{"a/docs/_build/", true},
 		{"a/dasdocs/_build-vsdoc.js", true},
 		{"a/dasdocs/_build-vsdoc.j", false},
+
+		// Override: Git/GitHub/Gitea-related paths should NOT be detected as vendored
+		{".gitignore", false},
+		{".gitattributes", false},
+		{".gitmodules", false},
+		{"src/.gitignore", false},
+		{".github/workflows/ci.yml", false},
+		{".gitea/workflows/ci.yml", false},
 	}
 	for _, tt := range tests {
 		t.Run(tt.path, func(t *testing.T) {