[clang-tools-extra] [llvm] [llvm] add support for mustache templating language (PR #105893)

[Nicolas van Kempen via llvm-commits]

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+//===--- Mustache.h ---------------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Implementation of the Mustache templating language supports version 1.4.2
+// currently relies on llvm::json::Value for data input
+// See the Mustache spec for more information
+// (https://mustache.github.io/mustache.5.html).
+//
+// Current Features Supported:
+// - Variables
+// - Sections
+// - Inverted Sections
+// - Partials
+// - Comments
+// - Lambdas
+// - Unescaped Variables
+//
+// Features Not Supported:
+// - Set Delimiter
+// - Blocks
+// - Parents
+// - Dynamic Names
+//
+// The Template class is container class outputs the Mustache template string
+// and is main class for users. It stores all the lambdas and the ASTNode Tree.
+// When the Template is instantiated it tokenize the Template String and
+// creates a vector of Tokens. Then it calls a basic recursive descent parser
+// to construct the ASTNode Tree. The ASTNodes are all stored in an arena
+// allocator which is freed once the template class goes out of scope
+//
+// Usage:
----------------
nicovank wrote:

Usage is now stream-based, right?

https://github.com/llvm/llvm-project/pull/105893