threading: add force-client-threads option

This patch adds a config option to force the use of client side threads.
This option will override a servers Thread capability, and only build
threads on the client. It can be enabled contextually. For example:

	[ui]
	threading-enabled = true

	[ui:folder~^Archive]
	force-client-threads = true

This config would enable threads for all views, and use client threads
for folders that start with Archive. This can be advantageous if, for
example, the folder is very large and the server has a slow response due
to building threads for the entire mailbox

Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Robin Jarry <robin@jarry.cc>

config/aerc.conf

@@ -174,6 +174,11 @@ completion-popovers=true
 # Default: false
 #threading-enabled=false
 
+# Force client-side thread building
+#
+# Default: false
+#force-client-threads=false
+
 [statusline]
 # Describes the format string for the statusline.
 #

config/config.go

@@ -46,6 +46,7 @@ type UIConfig struct {
 	EmptyDirlist        string        `ini:"empty-dirlist"`
 	MouseEnabled        bool          `ini:"mouse-enabled"`
 	ThreadingEnabled    bool          `ini:"threading-enabled"`
+	ForceClientThreads  bool          `ini:"force-client-threads"`
 	FuzzyComplete       bool          `ini:"fuzzy-complete"`
 	NewMessageBell      bool          `ini:"new-message-bell"`
 	Spinner             string        `ini:"spinner"`

doc/aerc-config.5.scd

@@ -300,6 +300,12 @@ These options are configured in the *[ui]* section of aerc.conf.
 
 	Default: false
 
+*force-client-threads*
+	Force threads to be built client-side. Backends that don't support threading
+	will always build threads client side.
+
+	Default: false
+
 
 ## Contextual UI Configuration
 

lib/msgstore.go

@@ -60,13 +60,12 @@ type MessageStore struct {
 func NewMessageStore(worker *types.Worker,
 	dirInfo *models.DirectoryInfo,
 	defaultSortCriteria []*types.SortCriterion,
-	thread bool,
+	thread bool, clientThreads bool,
 	triggerNewEmail func(*models.MessageInfo),
 	triggerDirectoryChange func()) *MessageStore {
 
 	dirInfoUpdateDelay := 5 * time.Second
 
-	var clientThreads bool
 	if !dirInfo.Caps.Thread {
 		clientThreads = true
 	}

widgets/account.go

@@ -295,6 +295,7 @@ func (acct *AccountView) onMessage(msg types.WorkerMessage) {
 			store = lib.NewMessageStore(acct.worker, msg.Info,
 				acct.GetSortCriteria(),
 				acct.UiConfig().ThreadingEnabled,
+				acct.UiConfig().ForceClientThreads,
 				func(msg *models.MessageInfo) {
 					acct.conf.Triggers.ExecNewEmail(acct.acct,
 						acct.conf, msg)