samples: add rename_file.go sample

[nidhiii-27]

This pull request adds a new sample, rename_file.go, to the storage/objects directory.

This sample demonstrates how to use the new Move feature in the Go Google Cloud Storage client library to atomically rename an object within a bucket. The sample includes comments highlighting that this feature requires the Hierarchical Namespace feature to be enabled on the bucket.

[snippet-bot]

Here is the summary of changes.

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• storage/objects/rename_file.go:18, tag storage_rename_file

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[gemini-code-assist]

Summary of Changes

Hello @nidhiii-27, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new Go sample for Google Cloud Storage, focusing on the atomic renaming of objects. The primary goal is to provide a clear example of how to leverage the Move operation in the Go client library, while also informing users about the necessary prerequisite of having the Hierarchical Namespace feature enabled on their buckets for this functionality.

Highlights

• New Sample Added: A new Go sample file, rename_file.go, has been added to the storage/objects directory.
• Atomic Object Renaming: The sample demonstrates how to use the Google Cloud Storage client library's Move feature to atomically rename an object within a bucket.
• Hierarchical Namespace Requirement: The sample explicitly highlights that this atomic rename operation requires the Hierarchical Namespace feature to be enabled on the target bucket.

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[gemini-code-assist]

Code Review

This pull request introduces a new Go sample, rename_file.go, demonstrating how to atomically rename an object in a Google Cloud Storage bucket using the MoverFrom feature. The code is clear and follows the existing patterns in the repository.

My review includes two main points. First, I've noted that the new sample is missing corresponding tests. Adding a test case to objects_test.go is crucial for ensuring the sample's correctness and maintainability over time. Second, I suggest adding a precondition to the rename operation to prevent accidentally overwriting existing files, which makes the sample more robust and educational.

[gemini-code-assist]

This new sample function renameFile is not covered by any tests in objects_test.go. To ensure the sample works as expected and to prevent future regressions, please add a system test for it. This test should verify that the source object is removed and the destination object is created after the rename operation. Given that this feature requires Hierarchical Namespace to be enabled, the test setup might need to create a bucket with this feature specifically.

[gemini-code-assist]

For a more robust and idiomatic sample, it's good practice to demonstrate the use of preconditions to prevent race conditions or accidental data loss. In this case, you could add a DoesNotExist precondition on the destination object to prevent overwriting an existing file. This is a common and important pattern when renaming or moving files.

	src := client.Bucket(bucket).Object(srcObject)
	dst := client.Bucket(bucket).Object(destObject)

	// Optional: set a precondition to avoid potential race conditions and data
	// corruptions. The request to rename the file is aborted if the
	// destination object already exists.
	dst = dst.If(storage.Conditions{DoesNotExist: true})