Git rebase versus merge
31st December 2019
I’ve been thinking a lot about Git over the last 6 months since moving from a GUI to the command line. One thing I’ve heard a bit of noise about whether
git rebase is better than
git merge to get a branch up to date and pre-emptively fix any merge conflicts before a pull/merge request (PR) is raised.
With the application I used for Git, getting things up to date was as easy as dragging a branch (e.g.
master) onto the currently checked-out branch. This merged the changes in and highlighted any conflicts that arose. You can rebase in GUIs like Tower, but merging was so easy that I never really felt the need to take it for a test run. Merging is what I always did, and so continued to do when I moved to the command line.
Now that I’ve been using the command line for Git for over 6 months, I’ve begun to think differently about using
merge like that. Maybe
rebase is better. Here’s a quick run-down of the pros and cons of each.
Pros of merging
- Easy to push and pull to/from remote
- Respects the timeline of when commits were made
- A personal one: conflicts are relatively straightforward to fix; mainly because I’m familiar with the process
Cons of merging
- Clutter – merging one branch into another creates a merge commit, so there will be merge commits whenever work has been merged in
- It can be difficult to find the new work with
git log, as the commits may be peppered amongst other work in the timeline; this is especially true if changes have been made sporadically over a long-ish running branch
Pros of rebasing
- Rebasing is tidy it doesn’t create merge commits, so there’s not clutter in the log
- It’s easy to see what has been done as it puts new work at the top of the
Cons of rebasing
- Rebasing rewrites history, so even if commits that are being merged in were made after those in the feature branch they’re placed before (under) them
- You can’t push commits to the remote as, after a rebase, the histories are different – a force push (
git push -f origin example-branch) is needed to which overwrite the history on the remote with that of the local
- Another personal one: fixing any conflicts is totally unfamiliar
Where I sit
For me, the big advantage of using
merge looks to be that I can quickly and easily see exactly what I’ve been doing with a
git log. Yes, it rewrites history, but it doesn’t change the time stamps on the commits, just the order that the commits appear in the log. Merging respects the timeline of when things were done, but I’m happy to sacrifice that authenticity in the name of tidiness and scanability.
My main issue is unfamiliarity with rebasing, so I’m going to use it for a while and see how I get on. Maybe I’ll end up going back to merging, maybe I’ll find some more subtle advantages to rebasing and it’ll stick. I’ll keep you posted!
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