Change allow_vendor_change default to false with descriptive hint

- Change the default value of `allow_vendor_change` from `true` to `false` so packages stick to
their original vendor during upgrades (rpm-software-management#712)
- When the solver blocks an update due to a vendor change restriction, print a hint suggesting
`--setopt=allow_vendor_change=true` (rpm-software-management#750)

A previous attempt to change this default was reverted because solver errors gave no indication
that vendor locking was the cause. The new hint in `print_resolve_hints()` addresses that by
detecting `RULE_UPDATE` problems and telling the user how to override the restriction.

Closes: rpm-software-management#712 rpm-software-management#750 SWMBZBUGSM-153 BZ#2219624

CI Tests: rpm-software-management/ci-dnf-stack#1839

Signed-off-by: Fellipe Henrique <me@fhbash.com>

Author: fhbash

dnf5/main.cpp

@@ -1107,6 +1107,7 @@ static void print_resolve_hints(dnf5::Context & context) {
         bool conflict = false;
         bool broken_file_dep = false;
         bool best = false;
+        bool vendor_change = false;
         // walk through all solver problem to detect a conflict, missing file dependency and best
         for (const auto & resolve_log : context.get_transaction()->get_resolve_logs()) {
             if (resolve_log.get_problem() == libdnf5::GoalProblem::SOLVER_ERROR) {
@@ -1129,6 +1130,9 @@ static void print_resolve_hints(dnf5::Context & context) {
                             case libdnf5::ProblemRules::RULE_BEST_2:
                                 best = true;
                                 break;
+                            case libdnf5::ProblemRules::RULE_UPDATE:
+                                vendor_change = true;
+                                break;
                             default:
                                 break;
                         }
@@ -1151,6 +1155,11 @@ static void print_resolve_hints(dnf5::Context & context) {
             }
         }
 
+        if (!conf.get_allow_vendor_change_option().get_value() && vendor_change) {
+            const std::string_view arg{"--setopt=allow_vendor_change=true"};
+            hints.emplace_back(libdnf5::utils::sformat(_("{} to allow changing package vendors"), arg));
+        }
+
         if (broken_file_dep) {
             const std::string_view arg{"--setopt=optional_metadata_types=filelists"};
             auto optional_metadata = conf.get_optional_metadata_types_option().get_value();

doc/dnf5.conf.5.rst

@@ -60,7 +60,7 @@ repository configuration file should aside from repo ID consists of baseurl, met
     If disabled, DNF5 will stick to the original vendor during RPM upgrades or downgrades.
     This preference, however, can be fine-tuned using :ref:`Vendor change policies <dnf5_vendor_change_policy-label>`.
 
-    Default: ``True``.
+    Default: ``False``.
 
     .. WARNING:: This option is currently not supported for `downgrade` and `distro-sync` commands
 

libdnf5/conf/config_main.cpp

@@ -165,7 +165,7 @@ class ConfigMain::Impl {
     OptionBool gpgkey_dns_verification{false};
     OptionBool obsoletes{true};
     OptionBool exit_on_lock{false};
-    OptionBool allow_vendor_change{true};
+    OptionBool allow_vendor_change{false};
     OptionSeconds metadata_timer_sync{60 * 60 * 3};  // 3 hours
     OptionStringList disable_excludes{std::vector<std::string>{}};
     OptionEnum multilib_policy{"best", {"best", "all"}};  // :api

libdnf5/rpm/solv/goal_private.hpp

@@ -205,7 +205,7 @@ class GoalPrivate {
 
     bool allow_downgrade{true};
     bool allow_erasing{false};
-    bool allow_vendor_change{true};
+    bool allow_vendor_change{false};
     bool install_weak_deps{true};
     // Remove SOLVER_WEAK and add SOLVER_BEST to all jobs
     bool run_in_strict_mode{false};