[clang-format] Fix handling of ## comments in TextProto

[HazardyKnusperkeks]

Summary

As @krasimir said in D92257 the old behavior is buggy.

• Added checks for ##, ###, and ####.
• Adapted the test.
• Removed the check for TextProto, which is already in getLineCommentIndentPrefix.

clang/lib/Format/BreakableToken.cpp

for (size_t i = FirstLineIndex, e = Lines.size(); i < e; ++i) {
         else if (Prefix[i] == "///")
           Prefix[i] = "/// ";
         else if (Prefix[i] == "//!")
           Prefix[i] = "//! ";
         else if (Prefix[i] == "///<")
           Prefix[i] = "///< ";
         else if (Prefix[i] == "//!<")
           Prefix[i] = "//!< ";
-        else if (Prefix[i] == "#" &&
-                 Style.Language == FormatStyle::LK_TextProto)
+        else if (Prefix[i] == "#")
           Prefix[i] = "# ";
+        else if (Prefix[i] == "##")
+          Prefix[i] = "## ";
+        else if (Prefix[i] == "###")
+          Prefix[i] = "### ";
+        else if (Prefix[i] == "####")
+          Prefix[i] = "#### ";
       }
 
       Tokens[i] = LineTok;
       Content[i] = Lines[i].substr(IndentPrefix.size());
       OriginalContentColumn[i] =
           StartColumn + encoding::columnWidthWithTabs(OriginalPrefix[i],
                                                       StartColumn,
                                                       Style.TabWidth, Encoding);

clang/unittests/Format/FormatTestTextProto.cpp

verifyFormat("aaaaaaaaaa: 100\n"
                "# Single line comment for stuff here.\n"
                "cccccccccccccccccccccccc: 3849\n"
                "# Multiline comment for stuff here.\n"
                "# Multiline comment for stuff here.\n"
                "# Multiline comment for stuff here.\n"
                "cccccccccccccccccccccccc: 3849");
 }
 
-TEST_F(FormatTestTextProto, UnderstandsHashHashComments) {
+TEST_F(FormatTestTextProto, UnderstandsHashComments) {
   FormatStyle Style = getGoogleStyle(FormatStyle::LK_TextProto);
   Style.ColumnLimit = 60; // To make writing tests easier.
   EXPECT_EQ("aaa: 100\n"
-            "##this is a double-hash comment.\n"
+            "## this is a double-hash comment.\n"
             "bb: 100\n"
             "## another double-hash comment.\n"
             "### a triple-hash comment\n"
             "cc: 200\n"
+            "### another triple-hash comment\n"
             "#### a quadriple-hash comment\n"
-            "dd: 100\n",
+            "dd: 100\n"
+            "#### another quadriple-hash comment\n",
             format("aaa: 100\n"
                    "##this is a double-hash comment.\n"
                    "bb: 100\n"
                    "## another double-hash comment.\n"
-                   "### a triple-hash comment\n"
+                   "###a triple-hash comment\n"
                    "cc: 200\n"
-                   "#### a quadriple-hash comment\n"
-                   "dd: 100\n",
+                   "### another triple-hash comment\n"
+                   "####a quadriple-hash comment\n"
+                   "dd: 100\n"
+                   "#### another quadriple-hash comment\n",
                    Style));
 }
 
 TEST_F(FormatTestTextProto, FormatsExtensions) {
   verifyFormat("[type] { key: value }");
   verifyFormat("[type] {\n"
                "  keyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy: value\n"
                "}");