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/up.go

@@ -16,13 +16,13 @@ import (
 func runStepUp(
 	cmd *cobra.Command, opts *cli.Options, steps int, create bool,
 ) (err error) {
-	m, db, err := openMigrator(cmd, opts, true, create)
+	migrator, db, err := openMigrator(cmd, opts, true, create)
 	if err != nil {
 		return err
 	}
 	defer closeDB(db, &err)
 
-	results, err := store.StepUp(cmd.Context(), m, int(steps))
+	results, err := store.StepUp(cmd.Context(), migrator, int(steps))
 
 	if len(results) == 0 && err == nil {
 		_, err := fmt.Fprintln(cmd.OutOrStdout(), "No changes made to database (up-to-date)")
@@ -37,7 +37,7 @@ func runStepUp(
 		return failure(cmd.OutOrStdout(), err)
 	}
 
-	return printVersion(cmd.Context(), cmd.OutOrStdout(), m)
+	return printVersion(cmd.Context(), cmd.OutOrStdout(), migrator)
 }
 
 func commandUp(opts *cli.Options) *cobra.Command {