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/common_test.go

@@ -16,7 +16,9 @@ import (
 
 func result(path, direction string) *goose.MigrationResult {
 	return &goose.MigrationResult{
-		Source:    &goose.Source{Path: "migrations/" + path},
+		Source: &goose.Source{
+			Path: "migrations/" + path,
+		},
 		Direction: direction,
 		Duration:  1500 * time.Microsecond,
 	}
@@ -45,7 +47,9 @@ func TestFailurePartial(t *testing.T) {
 }
 
 func TestFailureWithoutFailedSource(t *testing.T) {
-	err := failure(&bytes.Buffer{}, &goose.PartialError{Err: errors.New("boom")})
+	err := failure(&bytes.Buffer{}, &goose.PartialError{
+		Err: errors.New("boom"),
+	})
 	if err == nil || !strings.Contains(err.Error(), "unknown migration") {
 		t.Errorf("err = %v, want unknown migration", err)
 	}