Learn Git in a Day

Why Your Branch Falls Behind

Imagine this situation: you create a branch called feature/absolute from main and start working on a new feature. Meanwhile, a teammate finishes their own work and merges it into main. Now main has moved forward with new commits, and your branch is still based on the older version of main - the one from before your teammate's changes.

Here's what the history looks like at this point, before any merge or rebase:

      C---D  feature/absolute
     /
A---B---E  main

You branched off at B and made commits C and D. Meanwhile, your teammate added commit E to main. The two branches have diverged.

When you're done and try to merge your branch back into main, Git needs to combine two different histories: the commits your teammate added and the commits you added. To do this, Git creates what's called a merge commit - a special commit whose only purpose is to tie these two histories together. It doesn't contain any new code of its own; it just says "these two lines of work are now joined."

Here's what the history looks like after a merge:

      C---D  feature/absolute
     /     \
A---B---E---M  main

A and B are commits that existed before you created your branch. You branched off at B and made commits C and D on feature/absolute. Meanwhile, your teammate added commit E