internal/rpmmd: log repository files loaded during composer startup

This is a confusing part of the startup process. We have changed the naming
and we also added the cross distro building feature. It is unclear which
files are loaded and from where (if /etc or /usr).

Log the files that are loaded so every user can clearly see what
configuration osbuild-composer uses. This complements the log of loaded
configuration.

internal/rpmmd/repository.go

@@ -267,11 +267,14 @@ func LoadAllRepositories(confPaths []string) (DistrosRepoConfigs, error) {
 					continue
 				}
 
-				distroRepos, err := loadRepositoriesFromFile(filepath.Join(reposPath, fileEntry.Name()))
+				configFile := filepath.Join(reposPath, fileEntry.Name())
+				distroRepos, err := loadRepositoriesFromFile(configFile)
 				if err != nil {
 					return nil, err
 				}
 
+				log.Println("Loaded repository configuration file:", configFile)
+
 				distrosRepoConfigs[distro] = distroRepos
 			}
 		}