fileserver: Improve file hiding logic for directories and prefixes

Now, a filename to hide that is specified without a path separator will
count as hidden if it appears in any component of the file path (not
only the last component); semantically, this means hiding a file by only
its name (without any part of a path) will hide both files and folders,
e.g. hiding ".git" will hide "/.git" and also "/.git/foo".

We also do prefix matching so that hiding "/.git" will hide "/.git"
and "/.git/foo" but not "/.gitignore".

The remaining logic is a globular match like before.

modules/caddyhttp/fileserver/staticfiles_test.go

@@ -93,9 +93,78 @@ func TestSanitizedPathJoin(t *testing.T) {
 		}
 		actual := sanitizedPathJoin(tc.inputRoot, u.Path)
 		if actual != tc.expect {
-			t.Errorf("Test %d: [%s %s] => %s (expected %s)", i, tc.inputRoot, tc.inputPath, actual, tc.expect)
+			t.Errorf("Test %d: [%s %s] => %s (expected %s)",
+				i, tc.inputRoot, tc.inputPath, actual, tc.expect)
 		}
 	}
 }
 
-// TODO: test fileHidden
+func TestFileHidden(t *testing.T) {
+	for i, tc := range []struct {
+		inputHide []string
+		inputPath string
+		expect    bool
+	}{
+		{
+			inputHide: nil,
+			inputPath: "",
+			expect:    false,
+		},
+		{
+			inputHide: []string{".gitignore"},
+			inputPath: "/.gitignore",
+			expect:    true,
+		},
+		{
+			inputHide: []string{".git"},
+			inputPath: "/.gitignore",
+			expect:    false,
+		},
+		{
+			inputHide: []string{"/.git"},
+			inputPath: "/.gitignore",
+			expect:    false,
+		},
+		{
+			inputHide: []string{".git"},
+			inputPath: "/.git",
+			expect:    true,
+		},
+		{
+			inputHide: []string{".git"},
+			inputPath: "/.git/foo",
+			expect:    true,
+		},
+		{
+			inputHide: []string{".git"},
+			inputPath: "/foo/.git/bar",
+			expect:    true,
+		},
+		{
+			inputHide: []string{"/prefix"},
+			inputPath: "/prefix/foo",
+			expect:    true,
+		},
+		{
+			inputHide: []string{"/foo/*/bar"},
+			inputPath: "/foo/asdf/bar",
+			expect:    true,
+		},
+		{
+			inputHide: []string{"/foo"},
+			inputPath: "/foo",
+			expect:    true,
+		},
+		{
+			inputHide: []string{"/foo"},
+			inputPath: "/foobar",
+			expect:    false,
+		},
+	} {
+		actual := fileHidden(tc.inputPath, tc.inputHide)
+		if actual != tc.expect {
+			t.Errorf("Test %d: Is %s hidden in %v? Got %t but expected %t",
+				i, tc.inputPath, tc.inputHide, actual, tc.expect)
+		}
+	}
+}