Naming, layout and comments: descriptive full-word names, one item per line in wrapped calls and literals, and doc comments on exported names

Short and single-letter names in application code become full words (tests
keep theirs). Wrapped calls, signatures and composite literals put one item
per line, and one-line function bodies are expanded. Exported names and
groups of constants get doc comments, and comments refer to the renamed
identifiers.

internal/cli/migrate/down.go

@@ -32,13 +32,13 @@ confirmed by providing -yes.`,
 			yes, _ := cmd.Flags().GetBool("yes")
 			steps, _ := cmd.Flags().GetUint("steps")
 
-			m, db, err := openMigrator(cmd, opts, false, false)
+			migrator, db, err := openMigrator(cmd, opts, false, false)
 			if err != nil {
 				return err
 			}
 			defer closeDB(db, &err)
 
-			results, err := store.StepDown(cmd.Context(), m, int(steps), yes)
+			results, err := store.StepDown(cmd.Context(), migrator, int(steps), yes)
 
 			if len(results) == 0 && err == nil {
 				fmt.Println("No changes made to database (empty)")
@@ -58,7 +58,7 @@ confirmed by providing -yes.`,
 				return failure(cmd.OutOrStdout(), err)
 			}
 
-			return printVersion(cmd.Context(), cmd.OutOrStdout(), m)
+			return printVersion(cmd.Context(), cmd.OutOrStdout(), migrator)
 		},
 	}
 	cmd.Flags().Uint(