Use TaskChampion 0.7.0, now via cxx instead of hand-rolled FFI (#3588)

TC 0.7.0 introduces a new `TaskData` type that maps to Taskwarrior's
`Task` type more cleanly. It also introduces the idea of gathering lists
of operations and "committing" them to a replica.

A consequence of this change is that TaskChampion no longer
automatically maintains dependency information, so Taskwarrior must do
so, with its `TDB2::dependency_sync` method. This method does a very
similar thing to what TaskChampion had been doing, so this is a shift of
responsibility but not a major performance difference.

Cxx is .. not great. It is missing a lot of useful things that make a
general-purpose bridge impractical:

 - no support for trait objects
 - no support for `Option<T>` (https://github.com/dtolnay/cxx/issues/87)
 - no support for `Vec<Box<..>>`

As a result, some creativity is required in writing the bridge, for
example returning a `Vec<OptionTaskData>` from `all_task_data` to allow
individual `TaskData` values to be "taken" from the vector.

That said, Cxx is the current state-of-the-art, and does a good job of
ensuring memory safety, at the cost of some slightly awkward APIs.

Subsequent work can remove the "TDB2" layer and allow commands and other
parts of Taskwarrior to interface directly with the `Replica`.

src/commands/CMakeLists.txt

@@ -1,8 +1,6 @@
 cmake_minimum_required (VERSION 3.22)
 include_directories (${CMAKE_SOURCE_DIR}
                      ${CMAKE_SOURCE_DIR}/src
-                     ${CMAKE_SOURCE_DIR}/src/tc
-                     ${CMAKE_SOURCE_DIR}/src/tc/lib
                      ${CMAKE_SOURCE_DIR}/src/commands
                      ${CMAKE_SOURCE_DIR}/src/columns
                      ${CMAKE_SOURCE_DIR}/src/libshared/src
@@ -61,6 +59,7 @@ set (commands_SRCS Command.cpp        Command.h
                    CmdVersion.cpp     CmdVersion.h)
 
 add_library (commands STATIC ${commands_SRCS})
+target_link_libraries(commands taskchampion-cpp)
 
 #SET(CMAKE_BUILD_TYPE gcov)
 #SET(CMAKE_CXX_FLAGS_GCOV "--coverage")

src/commands/CmdImport.h

@@ -31,6 +31,7 @@
 #include <JSON.h>
 
 #include <string>
+#include <unordered_map>
 
 class CmdImport : public Command {
  public:

src/commands/CmdSync.cpp

@@ -35,12 +35,11 @@
 #include <inttypes.h>
 #include <shared.h>
 #include <signal.h>
+#include <taskchampion-cpp/lib.h>
 #include <util.h>
 
 #include <sstream>
 
-#include "tc/Server.h"
-
 ////////////////////////////////////////////////////////////////////////////////
 CmdSync::CmdSync() {
   _keyword = "synchronize";
@@ -60,56 +59,53 @@ CmdSync::CmdSync() {
 int CmdSync::execute(std::string& output) {
   int status = 0;
 
-  tc::Server server;
-  std::string server_ident;
+  Context& context = Context::getContext();
+  auto& replica = context.tdb2.replica();
+  std::stringstream out;
+  bool avoid_snapshots = false;
+  bool verbose = Context::getContext().verbose("sync");
 
   // If no server is set up, quit.
   std::string origin = Context::getContext().config.get("sync.server.origin");
   std::string url = Context::getContext().config.get("sync.server.url");
   std::string server_dir = Context::getContext().config.get("sync.local.server_dir");
+  std::string client_id = Context::getContext().config.get("sync.server.client_id");
   std::string gcp_credential_path = Context::getContext().config.get("sync.gcp.credential_path");
   std::string gcp_bucket = Context::getContext().config.get("sync.gcp.bucket");
   std::string encryption_secret = Context::getContext().config.get("sync.encryption_secret");
 
   // sync.server.origin is a deprecated synonym for sync.server.url
   std::string server_url = url == "" ? origin : url;
-
-  if (server_dir != "") {
-    server = tc::Server::new_local(server_dir);
-    server_ident = server_dir;
-  } else if (gcp_bucket != "") {
-    if (encryption_secret == "") {
-      throw std::string("sync.encryption_secret is required");
-    }
-    server = tc::Server::new_gcp(gcp_bucket, gcp_credential_path, encryption_secret);
-    std::ostringstream os;
-    os << "GCP bucket " << gcp_bucket;
-    server_ident = os.str();
-  } else if (server_url != "") {
-    std::string client_id = Context::getContext().config.get("sync.server.client_id");
-    if (client_id == "" || encryption_secret == "") {
-      throw std::string("sync.server.client_id and sync.encryption_secret are required");
-    }
-    server = tc::Server::new_sync(server_url, client_id, encryption_secret);
-    std::ostringstream os;
-    os << "Sync server at " << server_url;
-    server_ident = os.str();
-  } else {
-    throw std::string("No sync.* settings are configured. See task-sync(5).");
-  }
-
-  std::stringstream out;
   if (origin != "") {
     out << "sync.server.origin is deprecated. Use sync.server.url instead.\n";
   }
 
-  if (Context::getContext().verbose("sync")) {
-    out << format("Syncing with {1}", server_ident) << '\n';
+  if (server_dir != "") {
+    if (verbose) {
+      out << format("Syncing with {1}", server_dir) << '\n';
+    }
+    replica->sync_to_local(server_dir, avoid_snapshots);
+  } else if (gcp_bucket != "") {
+    if (encryption_secret == "") {
+      throw std::string("sync.encryption_secret is required");
+    }
+    if (verbose) {
+      out << format("Syncing with GCP bucket {1}", gcp_bucket) << '\n';
+    }
+    replica->sync_to_gcp(gcp_bucket, gcp_credential_path, encryption_secret, avoid_snapshots);
+  } else if (server_url != "") {
+    if (client_id == "" || encryption_secret == "") {
+      throw std::string("sync.server.client_id and sync.encryption_secret are required");
+    }
+    if (verbose) {
+      out << format("Syncing with sync server at {1}", server_url) << '\n';
+    }
+    replica->sync_to_remote(server_url, tc::uuid_from_string(client_id), encryption_secret,
+                            avoid_snapshots);
+  } else {
+    throw std::string("No sync.* settings are configured. See task-sync(5).");
   }
 
-  Context& context = Context::getContext();
-  context.tdb2.sync(std::move(server), false);
-
   if (context.config.getBoolean("purge.on-sync")) {
     context.tdb2.expire_tasks();
   }