git clear history

Git is a commonly used version control tool and is widely used in project development. During project development, we usually use various git commands for version control and management, including submitting code, merging branches, and other operations. However, in some cases, we may need to clear Git history, such as deleting sensitive information or clearing unnecessary commit records. Below we will discuss how to clear Git history.

1. Backup

Before performing the Git history clearing operation, we need to perform a backup to prevent errors or unexpected situations in the operation. It is important to back up the current code base to a safe place so that we can restore our code base if needed. We can use Git's packaging command to back up the project into a compressed file, for example:

git archive --format zip --output backup.zip HEAD

This command will package the current code base into a ZIP file and save it to backup.zip.

2. Clear the history record

1. Use the command to clear the history record of a single file

Deleting the history record of a single file is a relatively simple operation , we can use the following command to achieve:

$ git filter-branch --index-filter 'git rm --cached --ignore-unmatch path/to/file' --prune-empty -- --all

This command will completely delete the target file from the history record. Among them, path/to/file represents the file path to be cleared.

2. Use commands to clear commit history

Sometimes, we need to delete a commit and its subsequent history. To do this, we can use Git’s rebase command. Specifically, we need to perform the following steps:

1) Use the following command to display all commits in the project

$ git log --pretty=format:'%h %ad | %s%d [%an]' --graph --date=short

This command will display all commit records in the project.

2) Determine the SHA value of the commit to be cleared

We need to find the SHA value of the commit to be deleted, which can be obtained from the commit log below:

commit 55d4d98de4caf2ac1a8f783624c58e533500f3d7
Author: John Doe <john@doe.com>
Date:   Fri Apr 30 16:01:07 2021 -0700

    Added new feature

The above example The commit SHA value in is 55d4d98de4caf2ac1a8f783624c58e533500f3d7.

3) Use the following command to pop up the commit to be cleared

$ git rebase -i <commit-hash>^

For example, we want to delete the SHA value of 55d4d98de4caf2ac1a8f783624c58e53 3500f3d7 commit and its subsequent history, you can execute the following command:

$ git rebase -i 55d4d98de4caf2ac1a8f783624c58e533500f3d7^

4) Edit the interactive window to pop up the target commit

In interactive mode, we need to delete the The target commit is marked as "drop", then save the file and exit. An example looks like this:

pick 44a0c2c this is an invalid commit, which should be removed
drop 55d4d98 Added new feature

In the above example, the 55d4d98 history will be deleted, and the 44a0c2c history will become the latest commit.

5) Use the following command to clear old history records

$ git filter-branch --force --prune-empty --index-filter 'git rm -rf --cached --ignore-unmatch ./' --tag-name-filter cat -- --all

This command can clear the commit marked as "drop" and the commits after it.

6) Push to the remote warehouse

Finally, we need to force push to the remote warehouse to update the historical records in the remote warehouse and ensure the correctness of the historical records:

$ git push origin --force --all

Please note that you should exercise caution when executing the above command and ensure that you have backed up the code base. Because once deleted, it cannot be restored.

Summary

This article introduces how to use Git to clear history. Before performing these operations, we need to consider the consequences of historical record operations and make backups to avoid irreversible losses. At the same time, we should try to avoid clearing historical records and only use them when necessary.

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