[clang-diff] Refactor stop-after command-line flag

[jgravelle-google]

Summary

Rename stop-after to stop-after-topdown. When building LLVM with
-DLLVM_BUILD_LLVM_DYLIB=ON, stop-after collides with the stop-after
already present in LLVM.

This also refactors the flag to a boolean, to reflect that it can only
be in two states.

[johannes]

Looks good, thanks!
You can remove StopAfterTopDown from the ComparisonOptions struct definition

I have a second option stop-after option coming up but I will use another boolean for it, it is simpler this way.

[johannes]

Oh wait I get linker errors with BUILD_SHARED_LIBS=1

undefined reference to ClangDiffCategory in ASTDiff

[jgravelle-google]

If you have more stop-after options it'd probably be simpler to leave it as one field. I'll just rename it to "stop-diff-after" to avoid the name collision.

[jgravelle-google]

• Undo refactor, just change name

[johannes]

In D36989#848835, @jgravelle-google wrote:

If you have more stop-after options it'd probably be simpler to leave it as one field. I'll just rename it to "stop-diff-after" to avoid the name collision.

Ok, you can go ahead. Or, if I should do it let me know.

test/Tooling/clang-diff-topdown.cpp

 // RUN: %clang_cc1 -E %s > %t.src.cpp
 // RUN: %clang_cc1 -E %s > %t.dst.cpp -DDEST
-// RUN: clang-diff -dump-matches -stop-after=topdown %t.src.cpp %t.dst.cpp -- -std=c++11 | FileCheck %s
+// RUN: clang-diff -dump-matches -stop-diff-after=topdown %t.src.cpp %t.dst.cpp -- -std=c++11 | FileCheck %s
 //
 // Test the top-down matching of identical subtrees only.
 
 #ifndef DEST
 
 void f1()
 {
   // Match some subtree of height greater than 2.

tools/clang-diff/ClangDiff.cpp

static cl::opt<std::string> SourcePath(cl::Positional, cl::desc("<source>"),
                                        cl::Required,
                                        cl::cat(ClangDiffCategory));
 
 static cl::opt<std::string> DestinationPath(cl::Positional,
                                             cl::desc("<destination>"),
                                             cl::Optional,
                                             cl::cat(ClangDiffCategory));
 
-static cl::opt<std::string> StopAfter("stop-after",
+static cl::opt<std::string> StopAfter("stop-diff-after",
                                       cl::desc("<topdown|bottomup>"),
                                       cl::Optional, cl::init(""),
                                       cl::cat(ClangDiffCategory));
 
 static cl::opt<int> MaxSize("s", cl::desc("<maxsize>"), cl::Optional,
                             cl::init(-1), cl::cat(ClangDiffCategory));
 
 static cl::opt<std::string> BuildPath("p", cl::desc("Build path"), cl::init(""),