Understanding Duplicate File Change Commits in Git

Overview

Git’s handling of duplicate file change commits introduces a unique aspect of version control management, particularly when merging branches with identical changes.

This article explores a scenario in which identical file changes are merged twice, examining how Git manages commit history and why duplicate commits may occur under specific conditions.

Scenario Description

In a recent test, we followed these steps to observe Git’s behavior:

1. First Merge

• Initiated a merge operation with specific file changes.

• Approved the merge.

• Git created a new commit to record the merge, even though the changes were already present.

2. Second Merge

• Performed another merge with the same file changes, involving the same source and destination branches and same head revision.

• Approved and committed the changes using the merge label.

3. Repository Update

• The changes were pushed into the repository after clicking the Commit button.

• However, the content was already reflected from the first merge.

Understanding Git’s Behavior

Git permits the creation of duplicate commits under certain conditions:

1. Commit Creation Each merge, even with identical content, results in a distinct commit. Git records this as part of its linear commit history.

2. Head Revision Consideration If the merge operation uses an older revision, Git evaluates it based on timestamps. A new commit is created if the merged revision precedes the current HEAD.

Implications and Use Cases

1. Version Control Integrity Git ensures data integrity through commit hashes and timestamps, even when recording identical file changes across multiple commits.

2. Tool-Agnostic Behavior This behavior is consistent across environments—whether merges occur via command-line Git or integrated CI tools like AutoRABIT. Git remains robust and predictable.

Conclusion

Git’s flexibility in managing duplicate file change commits—especially under chronological discrepancies—reinforces its reliability as a version control system. Understanding these nuances allows teams to maintain accurate commit histories and effectively manage code across branches.