Add hardlink preserve support for Download and S2S sync operation

[dphulkar-msft]

Description

• Feature / Bug Fix: (Brief description of the feature or issue being addressed)

• Related Links:

• Issues

• Team thread

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• [Email Subject]

Type of Change

• Bug fix
• New feature
• Documentation update required
• Code quality improvement
• Other (describe):

How Has This Been Tested?

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[Copilot]

Pull request overview

This PR extends AzCopy’s hardlink preserve behavior to cover Download and S2S sync flows by teaching the source-side sync comparator to defer and then reconcile hardlink objects, and by tightening inode population for Azure Files/NFS traversals to avoid false hardlink grouping.

Changes:

• Populate NFS inode IDs only for true hardlinks (link count > 1) during Azure Files traversal.
• Add deferred hardlink reconciliation to the sync source comparator (used for Download and S2S sync) and ensure it runs during sync finalization.
• Update/expand NFS hardlink sync E2E scenarios and adjust sync comparator constructor call sites/tests.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
traverser/zc_traverser_file.go	Avoids setting inode on non-hardlinked NFS files to prevent incorrect grouping during sync comparisons.
azcopy/syncEnumerator.go	Wires up the updated sync source comparator and calls hardlink post-processing during finalize.
azcopy/syncComparator.go	Implements deferred processing for source hardlinks and adds group-structure/anchor logic for Download/S2S sync.
azcopy/syncProcessor.go	Ensures mirror-mode deletions treat hardlinks like deletable “files” on local targets.
cmd/zt_sync_file_file_test.go	Updates unit tests for the new sync comparator constructor signature.
e2etest/zt_newe2e_nfs_scenarios_test.go	Adjusts NFS scenario auth variations (OAuth commented out) and related scenario coverage.
e2etest/zt_newe2e_nfs_hardlink_sync_test.go	Adds fromTo-variant support and helpers for hardlink sync E2Es; OAuth commented out in variations.

Comments suppressed due to low confidence (1)

e2etest/zt_newe2e_nfs_scenarios_test.go:1597

• This scenario still includes OAuth as a destination credential type (line 1596) while OAuth is commented out elsewhere. If OAuth is intentionally disabled for NFS scenarios, remove it consistently here too; otherwise re-enable OAuth in the other variation lists so auth coverage is consistent across src/dst.

				src.(RemoteResourceManager).WithSpecificAuthType(
					ResolveVariation(svm, []ExplicitCredentialTypes{
						EExplicitCredentialType.SASToken(),
						//EExplicitCredentialType.OAuth(),
					}), svm, CreateAzCopyTargetOptions{}),
				dst.(RemoteResourceManager).WithSpecificAuthType(
					ResolveVariation(svm, []ExplicitCredentialTypes{
						EExplicitCredentialType.SASToken(),
						EExplicitCredentialType.OAuth(),
					}), svm, CreateAzCopyTargetOptions{}),

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