Add an advanced pref to control which pane is focused on split pane when using...

Add an advanced pref to control which pane is focused on split pane when using focus follows mouse. Issue 5780

sources/PseudoTerminal.m

@@ -5446,8 +5446,11 @@ ITERM_WEAKLY_REFERENCEABLE
     }
     [self fitTabsToWindow];
-    if (targetSession == [[self currentTab] activeSession] && ![iTermPreferences boolForKey:kPreferenceKeyFocusFollowsMouse]) {
-        [[self currentTab] setActiveSession:newSession];
+    if (targetSession == [[self currentTab] activeSession]) {
+        if (![iTermPreferences boolForKey:kPreferenceKeyFocusFollowsMouse] ||
+            [iTermAdvancedSettingsModel focusNewSplitPaneWithFocusFollowsMouse]) {
+            [[self currentTab] setActiveSession:newSession];
+        }
     }
     [[self currentTab] recheckBlur];
     [[self currentTab] numberOfSessionsDidChange];

sources/iTermAdvancedSettingsModel.h

@@ -187,5 +187,6 @@
 + (BOOL)tmuxUsesDedicatedProfile;
 + (BOOL)detectPasswordInput;
 + (BOOL)disablePasswordManagerAnimations;
++ (BOOL)focusNewSplitPaneWithFocusFollowsMouse;
 @end

sources/iTermAdvancedSettingsModel.m

@@ -179,7 +179,7 @@ DEFINE_BOOL(showSessionRestoredBanner, YES, @"Session: When restoring a session
 DEFINE_STRING(autoLogFormat,
               @"\\(session.creationTimeString).\\(session.name).\\(session.termid).\\(iterm2.pid).\\(session.autoLogId).log",
               @"Session: Format for automatic session log filenames.\nSee the Badges documentation for supported substitutions.");
-
+DEFINE_BOOL(focusNewSplitPaneWithFocusFollowsMouse, YES, @"Session: When focus follows mouse is enabled, should new split panes automatically be focused?");
 #pragma mark - Window