[clang-format] Don't reflow comment lines starting with '@'.

Summary:
This patch stops reflowing comment lines starting with '@', since they commonly
have a special meaning.

Reviewers: djasper

Reviewed By: djasper

Subscribers: cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D29323

llvm-svn: 293617
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 4d4b64b..7348fa0 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -2244,6 +2244,15 @@
                 "// long long long long\n"
                 "// ... --- ...",
                 getLLVMStyleWithColumns(20)));
+
+  // Don't reflow lines starting with '@'.
+  EXPECT_EQ("// long long long\n"
+            "// long\n"
+            "// @param arg",
+            format("// long long long long\n"
+                   "// @param arg",
+                   getLLVMStyleWithColumns(20)));
+
   // Reflow lines that have a non-punctuation character among their first 2
   // characters.
   EXPECT_EQ("// long long long\n"