Menu
When I work on two different features (on two different branches created from the master) it is quite annoying that I will not have the commit history when I proceed with merging.
I'll explain better. When I finish work on Branch-A, I merge it into master. And that's fine, if I git log I see all the commits I made on Branch-A.
Instead, when I finish work on Branch-B and I try to merge it to master (after that Branch-A has been already merged), I have to specify a commit message for the merging (while for the first branch I have not been asked anything).
And after the merging to master, if I type git log, I cannot see the commits of the Branch-B in the history of my master branch
Let's say I have
**Branch A**
commit 09b2unfas9d781n2e
Add more stuff
commit 8uj8masd89jas898a
Add stuff
**Branch B**
commit 09b2unfas9d781n2e
Add feature setting
commit 8uj8masd89jas898a
Add feature
I finish having
**Master**
commit 6hf6h8hd871udjkdn
Merge: 09b2un 34osd6
Merge branch 'Branch-B' into master
commit 09b2unfas9d781n2e
Add more stuff
commit 8uj8masd89jas898a
Add stuff
commit 34osd62dhc91123j8
I'm a previous commit from 'master'.
The last one before branching...
while I would like to obtain something like:
**Master**
commit 09b2unfas9d781n2e
Add feature setting
commit 8uj8masd89jas898a
Add feature
commit 09b2unfas9d781n2e
Add more stuff
commit 8uj8masd89jas898a
Add stuff
commit 34osd62dhc91123j8
I'm a previous commit from 'master'.
The last one before branching...
... that would reflect more exactly the history of the performed commits.
I don't get why I can keep the history from just one of the two branches.
How can I keep everything clear without those merge commits that hide/omit the real history of the merged commits?
798
Merging. When you run git merge , your HEAD branch will generate a new commit, preserving the ancestry of each commit history.
No, commits will only be added to the branch where they are committed. Git does nothing automatically that would alter the history of your code. If you want these commit merged to the main branch, you should have your teammate submit a new PR.
Some people keep a merge commit, even for a fast forward, because it keeps a very good record of when a branch was completed. These people prefer "complete and accurate" history over a "clean" history. Some people avoid merge commits, even rebasing their branches, because it keeps the history easier to read.
Rebase is one of two Git utilities that specializes in integrating changes from one branch onto another. The other change integration utility is git merge . Merge is always a forward moving change record. Alternatively, rebase has powerful history rewriting features.
It looks like the first merge was a fast-forward, and the second one was a three-way merge.
Explanation
Git has two versions of merge: fast-forward and three-way. (There are other versions, but that is not what happened here.) The default behavior is to do a fast-forward merge when possible, and otherwise do a three-way merge.
A fast-forward merge (you can force this behavior with the option --ff-only, which will cause the merge to fail when fast-forward is impossible) can take place when the commit that is being merged has the current position of the branch in its history. For example:
A - B - C - D <-master \ E - F - G <- branch-a Excecuting git merge (with default settings) will result in
A - B - C - D - E - F - G <- branch-a <-master You will also not get a chance to edit the merge commit because there is none. However, once this happens, your other branch will diverge from master (not just be ahead):
A - B - C - D - E - F - G <-master \ E1 - E2 <- branch-b Therefore, Git cannot just move the pointer of master from G to E2 because that will get rid of the changes that were made in F and G. Instead a three-way merge happens, which create a commit that has two parents, and also has a commit message. Now, master can be moved to this commit. (Notice that in this situation, master and branch-b do NOT point to the same commit.
A - B - C - D - E - F - G - H <-master \ / E1 - E2 <- branch-b If you want to have a linear history then you need to use rebase, but be forewarned that if anybody else has seen your branch commits this may lead to issues that are beyond the scope of this answer. Using rebase will involve two steps, rebasing and then fast-forward merge. So, instead of merging you first execute the following while on branch-b, git rebase master. This creates new commits that are copies of the old commits, i.e., the same change-set, author information and message, but new committer information and parent history. (I call the commits E1' and E2' in the illustration to indicate that they are just copies.) The old commits will exist until they are garbage collected, but will not be reachable unless you look at the reflog.)
A - B - C - D - E - F - G <-master \ \ E1 - E2 \ E1' - E2' <- branch-b Executing git checkout master; git merge --ff-only branch-b will now fast-forward your changes into master, thereby giving you a linear history.
A - B - C - D - E - F - G - E1' -E2' <-master <- branch-b Use rebase instead of merge. From the tutorial:
If you examine the log of a rebased branch, it looks like a linear history: it appears that all the work happened in series, even when it originally happened in parallel.
I imagine that the changes from your Branch-B cannot be merged using fast-forward merging into the master. In such cases a three-way-merge is done:
Instead of just moving the branch pointer forward, Git creates a new snapshot that results from this three-way merge and automatically creates a new commit that points to it. This is referred to as a merge commit, and is special in that it has more than one parent.
I would always rebase my commits before commiting them into the master to keep the linear history.
44
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
