offline: Use 90-99 part of the progress bar for scriptlets

This is definitely not exact (since there is no way to get the exact
number of scriptlets going to be executed), but is should at least show
some progress bar changes during the scriptlets execution.

dnf5/commands/offline/offline.cpp

@@ -133,7 +133,10 @@ class PlymouthTransCB : public RpmTransCB {
     void elem_progress(const libdnf5::base::TransactionPackage & item, uint64_t amount, uint64_t total) override {
         RpmTransCB::elem_progress(item, amount, total);
 
-        plymouth.progress(static_cast<int>(100 * static_cast<double>(amount) / static_cast<double>(total)));
+        if (total != 0) {
+            // Reserve the last 10% of the progress bar for post-transaction callbacks.
+            plymouth.progress(static_cast<int>(90 * static_cast<double>(amount) / static_cast<double>(total)));
+        }
 
         std::string action;
         switch (item.get_action()) {
@@ -187,10 +190,30 @@ class PlymouthTransCB : public RpmTransCB {
         const auto message = fmt::format(
             "Running {} scriptlet: {}...", script_type_to_string(type), to_full_nevra_string(nevra).c_str());
         plymouth.message(message);
+
+        if (type == ScriptType::POST_TRANSACTION) {
+            // Post-transaction scriptlets take a considerable amount of time,
+            // and there was no indication to the user that the process hadn't
+            // stalled. Let's try to utilize the 90-99% portion of the
+            // progress bar for them.
+            if (post_trans_scriptlets_count < post_trans_scriptlets_total) {
+                ++post_trans_scriptlets_count;
+            }
+            plymouth.progress(
+                90 + static_cast<int>(
+                         9 * static_cast<double>(post_trans_scriptlets_count) /
+                         static_cast<double>(post_trans_scriptlets_total)));
+        }
     }
 
 private:
     PlymouthOutput plymouth;
+    // Estimated total number of post-transaction scriptlets during a system
+    // upgrade (based on observations from F41).
+    // There is no reliable way to determine the exact number of scriptlets
+    // that will be executed.
+    const int post_trans_scriptlets_total = 40;
+    int post_trans_scriptlets_count = 0;
 };
 
 void OfflineCommand::pre_configure() {