What Is Meant by "First Parent" in a Git Commit?

When you use the git merge command to merge a branch/commit into your current branch, it joins their development histories together in a new commit. This new commit records both as its parents; the branch/commit you're merging in and the branch you are on when the merge occurs. The parent that gets recorded first (in the commit object of the new commit) is considered the "first parent", while the other one is considered the "second parent".

It is possible for a commit to have an arbitrary number of parents. This can happen, for example, when you git merge more than one branch/commit into your current branch. In such case, the hash of each parent is stored in the commit object, for example, like so:

# ...
parent 81c948a6488fc505be7eb22575a15e2db65c5d32
parent bdb425d2e0f76f30991f9c92c33fdfb9b09918ff
# ...

Typically, (in all popular git platforms) the parent that gets recorded first is the branch you were on when you merged. However, this behavior depends on the merge workflow specified in the repository, and can be different.

You can use the git show --first-parent or git log --first-parent command to follow the first parents only.

This post was published (and was last revised ) by Daniyal Hamid. Daniyal currently works as the Head of Engineering in Germany and has 20+ years of experience in software engineering, design and marketing. Please show your love and support by sharing this post.