clang-format: Add -disable-format option

When #27416 was fixed it
became impossible to only use clang-format for include sorting. Let's
introduce an option -disable-format to make it possible again to only
sort includes with clang-format without doing any other formatting.

Author: DaanDeMeyer

clang/docs/ClangFormat.rst

@@ -95,6 +95,8 @@ to format C/C++/Java/JavaScript/JSON/Objective-C/Protobuf/C# code.
                                      determined by the QualifierAlignment style flag
     --sort-includes                - If set, overrides the include sorting behavior
                                      determined by the SortIncludes style flag
+    --disable-format               - If set, only sort includes if include sorting
+                                     is enabled
     --style=<string>               - Set coding style. <string> can be:
                                      1. A preset: LLVM, GNU, Google, Chromium, Microsoft,
                                         Mozilla, WebKit.

clang/test/Format/disable-format-enable-include-sorting.cpp

@@ -0,0 +1,9 @@
+// RUN: clang-format %s -sort-includes -style=LLVM -disable-format | FileCheck %s
+
+#include <b>
+#include <a>
+// CHECK: <a>
+// CHECK-NEXT: <b>
+
+// CHECK: int *a  ;
+int *a  ;

clang/tools/clang-format/ClangFormat.cpp

@@ -120,6 +120,12 @@ static cl::opt<bool>
                           "determined by the SortIncludes style flag"),
                  cl::cat(ClangFormatCategory));
 
+static cl::opt<bool>
+    DisableFormat("disable-format",
+                  cl::desc("If set, only sort includes if include sorting\n"
+                           "is enabled"),
+                  cl::cat(ClangFormatCategory));
+
 static cl::opt<std::string> QualifierAlignment(
     "qualifier-alignment",
     cl::desc("If set, overrides the qualifier alignment style\n"
@@ -506,8 +512,11 @@ static bool format(StringRef FileName, bool ErrorOnIncompleteFormat = false) {
   // Get new affected ranges after sorting `#includes`.
   Ranges = tooling::calculateRangesAfterReplacements(Replaces, Ranges);
   FormattingAttemptStatus Status;
-  Replacements FormatChanges =
-      reformat(*FormatStyle, *ChangedCode, Ranges, AssumedFileName, &Status);
+  Replacements FormatChanges;
+  if (DisableFormat.getNumOccurrences() == 0 || !DisableFormat) {
+    FormatChanges =
+        reformat(*FormatStyle, *ChangedCode, Ranges, AssumedFileName, &Status);
+  }
   Replaces = Replaces.merge(FormatChanges);
   if (DryRun) {
     return Replaces.size() > (IsJson ? 1u : 0u) &&