Addon Manager: Make branch switching scarier

src/Mod/AddonManager/AddonManagerOptions.ui

@@ -284,6 +284,34 @@ of the line after a space (e.g. https://github.com/FreeCAD/FreeCAD master).</str
      </item>
     </layout>
    </item>
+   <item>
+    <widget class="QGroupBox" name="advanced">
+     <property name="sizePolicy">
+      <sizepolicy hsizetype="Minimum" vsizetype="Minimum">
+       <horstretch>0</horstretch>
+       <verstretch>0</verstretch>
+      </sizepolicy>
+     </property>
+     <property name="title">
+      <string>Advanced Options</string>
+     </property>
+     <layout class="QVBoxLayout" name="verticalLayout_3">
+      <item>
+       <widget class="Gui::PrefCheckBox" name="guiprefcheckboxShowBranchSwitcher">
+        <property name="text">
+         <string>Show option to change branches (Requires GitPython)</string>
+        </property>
+        <property name="prefEntry" stdset="0">
+         <string>ShowBranchSwitcher</string>
+        </property>
+        <property name="prefPath" stdset="0">
+         <string>Addons</string>
+        </property>
+       </widget>
+      </item>
+     </layout>
+    </widget>
+   </item>
    <item>
     <spacer name="verticalSpacer">
      <property name="orientation">

src/Mod/AddonManager/change_branch.py

@@ -96,6 +96,18 @@ class ChangeBranchDialog(QtWidgets.QWidget):
                 # This is the one we are already on... just return
                 return
 
+            result = QtWidgets.QMessageBox.critical(
+                self,
+                translate("AddonsInstaller", "DANGER: Developer feature"),
+                translate(
+                    "AddonsInstaller",
+                    "DANGER: Switching branches is intended for developers and beta testers, and may result in broken, non-backwards compatible documents, instability, crashes, and/or the premature heat death of the universe. Are you sure you want to continue?",
+                ),
+                QtWidgets.QMessageBox.Yes | QtWidgets.QMessageBox.Cancel,
+                QtWidgets.QMessageBox.Cancel,
+            )
+            if result == QtWidgets.QMessageBox.Cancel:
+                return
             if self.item_model.repo.is_dirty():
                 result = QtWidgets.QMessageBox.critical(
                     self,
@@ -107,7 +119,7 @@ class ChangeBranchDialog(QtWidgets.QWidget):
                     QtWidgets.QMessageBox.Yes | QtWidgets.QMessageBox.Cancel,
                     QtWidgets.QMessageBox.Cancel,
                 )
-                if result ==  QtWidgets.QMessageBox.Cancel:
+                if result == QtWidgets.QMessageBox.Cancel:
                     return
 
             if isinstance(ref, git.TagReference):

src/Mod/AddonManager/package_details.py

@@ -200,7 +200,10 @@ class PackageDetails(QWidget):
                 if repo.metadata:
                     installed_version_string += (
                         "<b>"
-                        + translate("AddonsInstaller", "On branch {}, update available to version").format(repo.branch)
+                        + translate(
+                            "AddonsInstaller",
+                            "On branch {}, update available to version",
+                        ).format(repo.branch)
                         + " "
                     )
                     installed_version_string += repo.metadata.Version
@@ -234,12 +237,18 @@ class PackageDetails(QWidget):
 
                 if detached_head:
                     installed_version_string += (
-                        translate("AddonsInstaller", "Git tag '{}' checked out, no updates possible").format(branch)
+                        translate(
+                            "AddonsInstaller",
+                            "Git tag '{}' checked out, no updates possible",
+                        ).format(branch)
                         + "."
                     )
                 else:
                     installed_version_string += (
-                        translate("AddonsInstaller", "This is the latest version available for branch {}").format(branch)
+                        translate(
+                            "AddonsInstaller",
+                            "This is the latest version available for branch {}",
+                        ).format(branch)
                         + "."
                     )
             elif status == AddonManagerRepo.UpdateStatus.PENDING_RESTART:
@@ -341,7 +350,7 @@ class PackageDetails(QWidget):
             self.ui.labelWarningInfo.show()
             self.ui.labelWarningInfo.setText(
                 "<h1>"
-                + translate("AddonsInstaller", "WARNING: This addon requires FreeCAD ") 
+                + translate("AddonsInstaller", "WARNING: This addon requires FreeCAD ")
                 + required_version
                 + "</h1>"
             )
@@ -362,7 +371,9 @@ class PackageDetails(QWidget):
             # it's possible that this package actually provides versions of itself
             # for newer and older versions
 
-            first_supported_version = self.repo.metadata.getFirstSupportedFreeCADVersion()
+            first_supported_version = (
+                self.repo.metadata.getFirstSupportedFreeCADVersion()
+            )
             if first_supported_version is not None:
                 required_version = first_supported_version.split(".")
                 fc_major = int(FreeCAD.Version()[0])
@@ -381,6 +392,11 @@ class PackageDetails(QWidget):
 
         self.ui.buttonChangeBranch.hide()
 
+        pref = FreeCAD.ParamGet("User parameter:BaseApp/Preferences/Addons")
+        show_switcher = pref.GetBool("ShowBranchSwitcher", False)
+        if not show_switcher:
+            return
+
         # Is this repo installed? If not, return.
         if self.repo.status() == AddonManagerRepo.UpdateStatus.NOT_INSTALLED:
             return