[www] List both the regular and expanded form of %diff in the
authorRichard Smith <richard@metafoo.co.uk>
Wed, 31 Mar 2021 00:21:31 +0000 (17:21 -0700)
committerRichard Smith <richard@metafoo.co.uk>
Wed, 31 Mar 2021 00:25:01 +0000 (17:25 -0700)
commitc23ee7718ea4f9292622af3d80efe2491eb2a506
treea52d97c151c2856ac56baaaa57f03aa422eda043
parent9ab677180091a690cd99d4ac55d5fb9e1149b1ec
[www] List both the regular and expanded form of %diff in the
diagnostics reference.

In passing, properly validate and diagnose errors in %diff format
specifiers.
clang/utils/TableGen/ClangDiagnosticsEmitter.cpp