Always use dart-git for merges

I'm going to be moving away from libgit2 for the next release, and while
my own dart-git's merging is quite bad in comparison to libgit2, it's
the only way to move forward without libgit2.

The cross-compilation and all is too much of a pain for me to continue
using it. I haven't had an iOS release in over a year because of it.
Plus it sucks all the fun out this project.

Fixes #934

lib/core/git_repo.dart

@@ -235,24 +235,11 @@ class GitNoteRepository {
       rethrow;
     }
 
-    if (useDartGit || AppConfig.instance.experimentalGitMerge) {
-      var author = GitAuthor(
-        email: config.gitAuthorEmail,
-        name: config.gitAuthor,
-      );
-      return repo.mergeCurrentTrackingBranch(author: author);
-    }
-
-    try {
-      await _gitRepo.merge(
-        branch: branchConfig.remoteTrackingBranch(),
-        authorEmail: config.gitAuthorEmail,
-        authorName: config.gitAuthor,
-      );
-    } on gb.GitException catch (ex, stackTrace) {
-      Log.e("Git Merge Failed", ex: ex, stacktrace: stackTrace);
-      rethrow;
-    }
+    var author = GitAuthor(
+      email: config.gitAuthorEmail,
+      name: config.gitAuthor,
+    );
+    return repo.mergeCurrentTrackingBranch(author: author);
   }
 
   Future<void> push() async {

lib/l10n/app_en.arb

@@ -137,7 +137,6 @@
   "settingsExperimentalAccounts": "Platform Independent Accounts",
   "settingsExperimentalIncludeSubfolders": "Include Subfolders",
   "settingsExperimentalExperimentalGitOps": "Dart-only Git implementation",
-  "settingsExperimentalMerge": "Dart-only merge implementation",
   "settingsExperimentalAutoCompleteTags": "Tags Auto Completion",
   "settingsExperimentalHistory": "History View",
   "settingsEditorsTitle": "Editor Settings",

lib/settings/app_config.dart

@@ -32,7 +32,6 @@ class AppConfig extends ChangeNotifier {
   var experimentalSubfolders = false;
   var experimentalMarkdownToolbar = false;
   var experimentalAccounts = false;
-  var experimentalGitMerge = false;
   var experimentalGitOps = false;
   var experimentalTagAutoCompletion = false;
 
@@ -55,8 +54,6 @@ class AppConfig extends ChangeNotifier {
         experimentalMarkdownToolbar;
     experimentalAccounts =
         pref.getBool("experimentalAccounts") ?? experimentalAccounts;
-    experimentalGitMerge =
-        pref.getBool("experimentalGitMerge") ?? experimentalGitMerge;
     experimentalGitOps =
         pref.getBool("experimentalGitOps") ?? experimentalGitOps;
     experimentalTagAutoCompletion =
@@ -85,8 +82,6 @@ class AppConfig extends ChangeNotifier {
         defaultSet.experimentalMarkdownToolbar);
     _setBool(pref, "experimentalAccounts", experimentalAccounts,
         defaultSet.experimentalAccounts);
-    _setBool(pref, "experimentalGitMerge", experimentalGitMerge,
-        defaultSet.experimentalGitMerge);
     _setBool(pref, "experimentalGitOps", experimentalGitOps,
         defaultSet.experimentalGitOps);
     _setBool(
@@ -112,7 +107,6 @@ class AppConfig extends ChangeNotifier {
       'debugLogLevel': debugLogLevel,
       'experimentalMarkdownToolbar': experimentalMarkdownToolbar.toString(),
       'experimentalAccounts': experimentalAccounts.toString(),
-      'experimentalGitMerge': experimentalGitMerge.toString(),
       'experimentalGitOps': experimentalGitOps.toString(),
       'experimentalTagAutoCompletion': experimentalTagAutoCompletion.toString(),
       'experimentalHistory': experimentalHistory.toString(),

lib/settings/settings_experimental.dart

@@ -73,15 +73,6 @@ class _ExperimentalSettingsScreenState
                 setState(() {});
               },
             ),
-            SwitchListTile(
-              title: Text(context.loc.settingsExperimentalMerge),
-              value: appConfig.experimentalGitMerge,
-              onChanged: (bool newVal) {
-                appConfig.experimentalGitMerge = newVal;
-                appConfig.save();
-                setState(() {});
-              },
-            ),
             SwitchListTile(
               title: Text(context.loc.settingsExperimentalExperimentalGitOps),
               value: appConfig.experimentalGitOps,