doc: Naming of source and debug repos

Resolves: #1355

doc/dnf5.conf.5.rst

@@ -587,6 +587,15 @@ Repo Options
 
     Default: ``True``.
 
+
+Source and debuginfo repository names
+=====================================
+
+For a given repository with an identifier in the form "<ID>-rpms", its corresponding source repository is expected to have an identifier in the form "<ID>-source-rpms" and debuginfo repository an identifier in the form "<ID>-debug-rpms". Otherwise (if the repository identifier doesn't have the "-rpms" suffix), the source repository is expected to have an identifier in the form "<ID>-source" and debuginfo repository an identifier in the form "<ID>-debuginfo".
+
+For example, for repository "fedora", the source repository is "fedora-source" and debuginfo repository is "fedora-debuginfo". For repository "fedora-rpms", the source repository is "fedora-source-rpms" and debuginfo repository is "fedora-debug-rpms".
+
+
 Repo Variables
 ==============
 

include/libdnf5/repo/repo_sack.hpp

@@ -139,6 +139,8 @@ class LIBDNF_API RepoSack : public sack::Sack<Repo> {
     libdnf5::BaseWeakPtr get_base() const;
 
     /// For each enabled repository enable corresponding source repository.
+    /// When repo ID has suffix -rpm then it enables <ID>-source-rpms
+    /// otherwise it enables <ID>-source
     /// @since 5.0
     void enable_source_repos();