How to Recover Per-Line Git Blame History After Line Endings Were Changed to CR?

Oh no! You’ve just realized that someone (maybe even yourself) has changed the line endings in your Git repository to CR (Carriage Return), and now your precious per-line Git blame history is gone! Don’t panic; we’ve got your back. In this article, we’ll guide you through the process of recovering that history and getting your Git blame game back on track.

What’s the Big Deal About Line Endings?

Before we dive into the recovery process, let’s quickly discuss why line endings are a thing in the first place. In the olden days, different operating systems used different characters to indicate the end of a line in a text file. Windows used CR+LF (Carriage Return + Line Feed), Unix-based systems used LF (Line Feed), and Macs used CR. This led to issues when collaborating on projects across different platforms.

To avoid these issues, Git allows you to configure the line endings for your repository. However, when someone changes the line endings without properly configuring Git, it can cause chaos, including the loss of per-line Git blame history.

The Problem: Lost Git Blame History

When you run `git blame` on a file, Git shows you the commit history for each line in the file. This is super useful for tracking changes and identifying who made them. However, when the line endings are changed, Git thinks the entire file has been rewritten, and the blame history is lost.

If you’ve tried running `git blame` after the line endings were changed, you might have seen something like this:

abcdef123 (author 2022-01-01 10:00:00 +0000 1) <whole file>

This output indicates that the entire file was rewritten in a single commit, which is not what you want to see.

The Solution: Recovering Per-Line Git Blame History

Fear not, dear Git user! We can recover the per-line Git blame history using a combination of Git commands and some creative problem-solving.

Step 1: Identify the Commit that Changed the Line Endings

First, you need to find the commit that changed the line endings. You can do this using `git log` and `git diff`:

git log -p -- -M --no-renames

This command shows you a patch-style log of commits, with the `-M` option detecting renames and copies. Look for the commit that changed the line endings.

Step 2: Check Out the Previous Commit

Once you’ve identified the problematic commit, check out the previous commit using:

git checkout HEAD~1

This will put you in a detached HEAD state, which is okay for our purposes.

Step 3: Create a New Branch with the Original Line Endings

Create a new branch from the previous commit, and then change the line endings back to their original state:

git checkout -b recovery-branch
git add .
git diff --cached --no-renames --ignore-space-at-eol --ignore-space-change > recovery.patch
git reset --hard
git apply recovery.patch

This creates a new branch, adds all changes, and then creates a patch that reverts the line ending changes. We then reset the branch to its original state and apply the patch.

Step 4: Rebase the Original Branch onto the New Branch

Rebase the original branch onto the new branch using:

git checkout original-branch
git rebase recovery-branch

This replays the commits from the original branch onto the new branch, preserving the original line endings.

Step 5: Verify the Per-Line Git Blame History

Finally, verify that the per-line Git blame history has been recovered by running:

git blame -l -p

This should show you the commit history for each line in the file, including the original authors and dates.

Tips and Variations

Here are some additional tips and variations to help you recover your per-line Git blame history:

• If you have multiple files affected, create a script to automate the process for each file.

• To avoid losing the original branch, create a temporary branch for the recovery process and then merge it into the original branch.

• Use `git filter-branch` instead of `git rebase` for a more comprehensive rewrite of the commit history.

• If you’re using Git 2.24 or later, you can use `git switch` instead of `git checkout` for a more intuitive workflow.

Conclusion

Recovering per-line Git blame history after line endings were changed to CR might seem like a daunting task, but with these step-by-step instructions, you should be able to get your Git blame game back on track. Remember to stay vigilant about line endings and configure your Git repository correctly to avoid this issue in the future.

Happy Git-ing, and may your per-line blame history be forever preserved!

Git Command	Description
git log -p -- -M --no-renames	Show patch-style log of commits, detecting renames and copies
git checkout HEAD~1	Check out the previous commit
git checkout -b recovery-branch	Create a new branch for recovery
git add .	Stage all changes
git diff --cached --no-renames --ignore-space-at-eol --ignore-space-change > recovery.patch	Create a patch that reverts line ending changes
git reset --hard	Reset the branch to its original state
git apply recovery.patch	Apply the patch to revert line ending changes
git rebase recovery-branch	Rebase the original branch onto the new branch
git blame -l -p	Verify per-line Git blame history

Frequently Asked Question

Line endings got you down? Don’t worry, we’ve got you covered! Here are some answers to common questions about recovering per-line git blame history after line endings were changed to CR.