[clang-format] Add BreakBeforeTemplateCloser option (#118046)

In clang-format, multiline templates have the `>` on the same line as
the last parameter:

```c++
template <
    typename Foo,
    typename Bar>
void foo() {
```

I would like to add an option to put the `>` on the next line, like
this:

```c++
template <
    typename Foo,
    typename Bar
>
void foo() {
```

An example of a large project that uses this style is NVIDIA's CUTLASS,
here is an example:


https://github.com/NVIDIA/cutlass/blob/main/include/cutlass/epilogue/dispatch_policy.hpp#L149-L156

My reasoning is that it reminds me of this style of braces:

```c++
if (foo()) {
    bar();
    baz();}
```

Most people agree this is better:

```c++
if (foo()) {
    bar();
    baz();
}
```

---------

Co-authored-by: Owen Pan <owenpiano@gmail.com>

1 files changed, 18 insertions, 6 deletions

diff --git a/clang/lib/Format/ContinuationIndenter.cpp b/clang/lib/Format/ContinuationIndenter.cpp
index 6f7d213..3e51b4aa 100644
--- a/clang/lib/Format/ContinuationIndenter.cpp
+++ b/clang/lib/Format/ContinuationIndenter.cpp
@@ -349,6 +349,13 @@ bool ContinuationIndenter::canBreak(const LineState &State) {
     }
   }
 
+  // Don't allow breaking before a closing brace of a block-indented braced list
+  // initializer if there isn't already a break.
+  if (Current.is(tok::r_brace) && Current.MatchingParen &&
+      Current.isBlockIndentedInitRBrace(Style)) {
+    return CurrentState.BreakBeforeClosingBrace;
+  }
+
   // Allow breaking before the right parens with block indentation if there was
   // a break after the left parens, which is tracked by BreakBeforeClosingParen.
   if (Style.AlignAfterOpenBracket == FormatStyle::BAS_BlockIndent &&
@@ -356,12 +363,8 @@ bool ContinuationIndenter::canBreak(const LineState &State) {
     return CurrentState.BreakBeforeClosingParen;
   }
 
-  // Don't allow breaking before a closing brace of a block-indented braced list
-  // initializer if there isn't already a break.
-  if (Current.is(tok::r_brace) && Current.MatchingParen &&
-      Current.isBlockIndentedInitRBrace(Style)) {
-    return CurrentState.BreakBeforeClosingBrace;
-  }
+  if (Style.BreakBeforeTemplateCloser && Current.is(TT_TemplateCloser))
+    return CurrentState.BreakBeforeClosingAngle;
 
   // If binary operators are moved to the next line (including commas for some
   // styles of constructor initializers), that's always ok.
@@ -414,6 +417,8 @@ bool ContinuationIndenter::mustBreak(const LineState &State) {
   }
   if (CurrentState.BreakBeforeClosingParen && Current.is(tok::r_paren))
     return true;
+  if (CurrentState.BreakBeforeClosingAngle && Current.is(TT_TemplateCloser))
+    return true;
   if (Style.Language == FormatStyle::LK_ObjC &&
       Style.ObjCBreakBeforeNestedBlockParam &&
       Current.ObjCSelectorNameParts > 1 &&
@@ -1243,6 +1248,9 @@ unsigned ContinuationIndenter::addTokenOnNewLine(LineState &State,
         Style.AlignAfterOpenBracket == FormatStyle::BAS_BlockIndent;
   }
 
+  if (PreviousNonComment && PreviousNonComment->is(TT_TemplateOpener))
+    CurrentState.BreakBeforeClosingAngle = Style.BreakBeforeTemplateCloser;
+
   if (CurrentState.AvoidBinPacking) {
     // If we are breaking after '(', '{', '<', or this is the break after a ':'
     // to start a member initializer list in a constructor, this should not
@@ -1379,6 +1387,10 @@ unsigned ContinuationIndenter::getNewLineColumn(const LineState &State) {
       State.Stack.size() > 1) {
     return State.Stack[State.Stack.size() - 2].LastSpace;
   }
+  if (Style.BreakBeforeTemplateCloser && Current.is(TT_TemplateCloser) &&
+      State.Stack.size() > 1) {
+    return State.Stack[State.Stack.size() - 2].LastSpace;
+  }
   if (NextNonComment->is(TT_TemplateString) && NextNonComment->closesScope())
     return State.Stack[State.Stack.size() - 2].LastSpace;
   // Field labels in a nested type should be aligned to the brace. For example