How can I selectively merge or pick changes from another branch in Git?
I had the exact same problem as mentioned by you above. But I found this clearer in explaining the answer.
Summary:
-
Check out the path(s) from the branch you want to merge,
$ git checkout source_branch -- <paths>... Hint: It also works without `--` like seen in the linked post. -
or to selectively merge hunks
$ git checkout -p source_branch -- <paths>...
Alternatively, use reset and then add with the option -p,
$ git reset <paths>...
$ git add -p <paths>...
-
Finally commit
$ git commit -m "'Merge' these changes"
You use the cherry-pick command to get individual commits from one branch.
If the change(s) you want are not in individual commits, then use the method shown here to split the commit into individual commits. Roughly speaking, you use git rebase -i to get the original commit to edit, then git reset HEAD^ to selectively revert changes, then git commit to commit that bit as a new commit in the history.
There is another nice method here in Red Hat Magazine, where they use git add --patch or possibly git add --interactive which allows you to add just parts of a hunk, if you want to split different changes to an individual file (search in that page for "split").
Having split the changes, you can now cherry-pick just the ones you want.
To selectively merge files from one branch into another branch, run
git merge --no-ff --no-commit branchX
where branchX is the branch you want to merge from into the current branch.
The --no-commit option will stage the files that have been merged by Git without actually committing them. This will give you the opportunity to modify the merged files however you want to and then commit them yourself.
Depending on how you want to merge files, there are four cases:
1) You want a true merge.
In this case, you accept the merged files the way Git merged them automatically and then commit them.
2) There are some files you don't want to merge.
For example, you want to retain the version in the current branch and ignore the version in the branch you are merging from.
To select the version in the current branch, run:
git checkout HEAD file1
This will retrieve the version of file1 in the current branch and overwrite the file1 automerged by Git.
3) If you want the version in branchX (and not a true merge).
Run:
git checkout branchX file1
This will retrieve the version of file1 in branchX and overwrite file1 auto-merged by Git.
4) The last case is if you want to select only specific merges in file1.
In this case, you can edit the modified file1 directly, update it to whatever you'd want the version of file1 to become, and then commit.
If Git cannot merge a file automatically, it will report the file as "unmerged" and produce a copy where you will need to resolve the conflicts manually.
To explain further with an example, let's say you want to merge branchX into the current branch:
git merge --no-ff --no-commit branchX
You then run the git status command to view the status of modified files.
For example:
git status
# On branch master
# Changes to be committed:
#
# modified: file1
# modified: file2
# modified: file3
# Unmerged paths:
# (use "git add/rm <file>..." as appropriate to mark resolution)
#
# both modified: file4
#
Where file1, file2, and file3 are the files git have successfully auto-merged.
What this means is that changes in the master and branchX for all those three files have been combined together without any conflicts.
You can inspect how the merge was done by running the git diff --cached;
git diff --cached file1
git diff --cached file2
git diff --cached file3
If you find some merge undesirable then you can
- edit the file directly
- save
git commit
If you don't want to merge file1 and want to retain the version in the current branch
Run
git checkout HEAD file1
If you don't want to merge file2 and only want the version in branchX
Run
git checkout branchX file2
If you want file3 to be merged automatically, don't do anything.
Git has already merged it at this point.
file4 above is a failed merge by Git. This means there are changes in both branches that occur on the same line. This is where you will need to resolve the conflicts manually. You can discard the merged done by editing the file directly or running the checkout command for the version in the branch you want file4 to become.
Finally, don't forget to git commit.
I don't like the above approaches. Using cherry-pick is great for picking a single change, but it is a pain if you want to bring in all the changes except for some bad ones. Here is my approach.
There is no --interactive argument you can pass to git merge.
Here is the alternative:
You have some changes in branch 'feature' and you want to bring some but not all of them over to 'master' in a not sloppy way (i.e. you don't want to cherry pick and commit each one)
git checkout feature
git checkout -b temp
git rebase -i master
# Above will drop you in an editor and pick the changes you want ala:
pick 7266df7 First change
pick 1b3f7df Another change
pick 5bbf56f Last change
# Rebase b44c147..5bbf56f onto b44c147
#
# Commands:
# pick = use commit
# edit = use commit, but stop for amending
# squash = use commit, but meld into previous commit
#
# If you remove a line here THAT COMMIT WILL BE LOST.
# However, if you remove everything, the rebase will be aborted.
#
git checkout master
git pull . temp
git branch -d temp
So just wrap that in a shell script, change master into $to and change feature into $from and you are good to go:
#!/bin/bash
# git-interactive-merge
from=$1
to=$2
git checkout $from
git checkout -b ${from}_tmp
git rebase -i $to
# Above will drop you in an editor and pick the changes you want
git checkout $to
git pull . ${from}_tmp
git branch -d ${from}_tmp