Set up CI with Azure Pipelines that checks that sources are clang-for…

…mat'd (#132)

This script runs clang-format on the sources, then runs git status --porcelain on the result, redirected to stderr. If any output goes to stderr, Azure Pipelines marks the build as failed, which enforces that no changes were made to the repo by the clang-format pass.

Resolves #88

README.md

@@ -31,7 +31,9 @@ soon as possible.)
 * Tests: **Coming soon.** We rely on three test suites: devcrt, tr1, and [libcxx][]. We need to replace our current test
 harness, which extensively uses Microsoft-internal machinery.
 
-* Continuous Integration: **Coming soon.** We need tests first.
+* Continuous Integration: **In progress.** We've set up Azure Pipelines to validate changes to the repository.
+However, that infrastructure requires manual review before building community-submitted pull requests, as we haven't
+yet hardened it against untrusted changes.
 
 * Contribution Guidelines: **Coming soon.** Working on the STL's code involves following many rules. We have codebase
 conventions, Standard requirements, Microsoft-specific requirements, binary compatibility (ABI) requirements, and more.

azure-devops/enforce-clang-format.cmd

@@ -0,0 +1,6 @@
+:: Copyright (c) Microsoft Corporation.
+:: SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+@echo off
+clang-format -style=file -i stl/inc/* stl/inc/cvt/* stl/inc/experimental/* stl/src/* 2>&1
+echo If your build fails here, you need to format the following files with clang-format 8.0.1.
+git status --porcelain 1>&2

azure-pipelines.yml

@@ -0,0 +1,10 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+pool: 'STL'
+
+steps:
+- task: BatchScript@1
+  inputs:
+    filename: 'azure-devops/enforce-clang-format.cmd'
+    failOnStandardError: true
+    displayName: 'Enforce clang-format'

docs/pull_request_template.md

@@ -9,8 +9,6 @@ README.md.
 - [ ] I understand README.md.
 - [ ] If this is a feature addition, that feature has been voted into the C++
   Working Draft.
-- [ ] Any code files edited have been processed by clang-format 8.0.1.
-  (The version is important because clang-format's behavior sometimes changes.)
 - [ ] Identifiers in any product code changes are properly `_Ugly` as per
   https://eel.is/c++draft/lex.name#3.1 .
 - [ ] Identifiers in test code changes are *not* `_Ugly`.