resolve-feature-branches.md

How to Resolve Feature Branches

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Whenever you start developing something new, it is considered good practice to commit these changes to a feature branch before you integrate them in master. This way, you can test these changes without corrupting master. Some branching models even require this workflow.

There are a few different ways how to resolve such a feature branch and integrate the changes in the originating branch which are discussed in this document.

Note: In the following examples we will always use master for the originating branch and topic/feature for the feature branch.

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rewrite feature branch history

git rebase is the method to keep your history linear. It is recommended to rebase before every merge on top of the latest master.

$ git lol
* 2985b6b (master) blah blah
* ebe0262 blah
| * cba1d40 (HEAD -> topic/feature) fixes issue with feature
| * 8b29f74 adds blah to feature
| * 7f295dd adds feature foo
|/
* 03f4f8d previous commit
* 62a0ee9 ...

$ git rebase master
First, rewinding head to replay your work on top of it...
Applying: adds feature foo
Applying: adds blah to feature
Applying: fixes issue with feature

$ git lol
* 76e29d1 (HEAD -> topic/feature) fixes issue with feature
* 5428f8d adds blah to feature
* 43d263e adds feature foo
* 2985b6b (master) blah blah
* ebe0262 blah
* 03f4f8d previous commit
* 62a0ee9 ...

Without the rebase, the history after a merge would be non-linear:

$ git checkout master
Switched to branch 'master'
$ git merge topic/feature
Merge made by the 'recursive' strategy.
 foo | 3 +++
 1 file changed, 3 insertions(+)
 create mode 100644 foo

$ git lol
*   f17ba26 (HEAD -> master) Merge branch 'topic/feature'
|\
| * cba1d40 (topic/feature) fixes issue with feature
| * 8b29f74 adds blah to feature
| * 7f295dd adds feature foo
* | 2985b6b blah blah
* | ebe0262 blah
|/
* 03f4f8d previous commit
* 62a0ee9 ...

You should also not hesitate to rewrite topic/feature history before you merge. This is usually achieved by interactive rebase'ing. Rewrite until the feature branch history looks good.

resolving methods

The history before the merge for all examples below looks like this:

* d2e7011 (HEAD -> topic/feature) fixes issue with feature
* f1a50c4 adds blah to feature
* 174ed5d adds feature foo
* 2985b6b (master) blah blah
* ebe0262 blah
* 03f4f8d previous commit
* 62a0ee9 ...

As you can see, topic/feature has already been rebased on master.

merge with fast-forward

The goal of this method is to have the resulting history look like as if the topic/feature branch commits were created directly on master.

$ git lol
* d2e7011 (HEAD -> topic/feature) fixes issue with feature
* f1a50c4 adds blah to feature
* 174ed5d adds feature foo
* 2985b6b (master) blah blah
* ebe0262 blah
* 03f4f8d previous commit
* 62a0ee9 ...

$ git checkout master
Switched to branch 'master'
$ git merge --ff-only topic/feature
Updating 2985b6b..c6121fd
Fast-forward
 foo | 3 +++
 1 file changed, 3 insertions(+)
 create mode 100644 foo

$ git lol
* c6121fd (HEAD -> master, topic/feature) fixes issue with feature
* fcbba2d adds blah to feature
* 2e09b2a adds feature foo
* 2985b6b blah blah
* ebe0262 blah
* 03f4f8d previous commit
* 62a0ee9 ...

As you can see from the resulting history, master has just been moved forward to the commit topic/feature sits on. That is where the name fast-forward comes from.

merge with merge commit

The relevant difference to the other methods is that you preserve topic/feature history.

$ git lol
* d2e7011 (HEAD -> topic/feature) fixes issue with feature
* f1a50c4 adds blah to feature
* 174ed5d adds feature foo
* 2985b6b (master) blah blah
* ebe0262 blah
* 03f4f8d previous commit
* 62a0ee9 ...

$ git checkout master
Switched to branch 'master'
$ git merge --no-ff --no-edit topic/feature
Merge made by the 'recursive' strategy.
 foo | 3 +++
 1 file changed, 3 insertions(+)
 create mode 100644 foo

$ git lol
*   4ea0082 (HEAD -> master) Merge branch 'topic/feature'
|\
| * c6121fd (topic/feature) fixes issue with feature
| * fcbba2d adds blah to feature
| * 2e09b2a adds feature foo
|/
* 2985b6b blah blah
* ebe0262 blah
* 03f4f8d previous commit
* 62a0ee9 ...

The history is still considered linear because all commits reside on one side of the branch, that is also why it is important to rebase first.

squash merge

This creates a single commit on top of master. All history of topic/feature gets condensed into a single commit. This way to resolve a feature branch should be used if the resulting diff is relatively small.

$ git lol
* d2e7011 (HEAD -> topic/feature) fixes issue with feature
* f1a50c4 adds blah to feature
* 174ed5d adds feature foo
* 2985b6b (master) blah blah
* ebe0262 blah
* 03f4f8d previous commit
* 62a0ee9 ...

$ git checkout master
Switched to branch 'master'
$ git merge --squash topic/feature
Updating 2985b6b..c6121fd
Fast-forward
Squash commit -- not updating HEAD
 foo | 3 +++
 1 file changed, 3 insertions(+)
 create mode 100644 foo
$ git commit -v
[master 66fcf8b] adds feature foo
 1 file changed, 3 insertions(+)
 create mode 100644 foo

$ git lol
* 66fcf8b (HEAD -> master) adds feature foo
| * c6121fd (topic/feature) fixes issue with feature
| * fcbba2d adds blah to feature
| * 2e09b2a adds feature foo
|/
* 2985b6b blah blah
* ebe0262 blah
* 03f4f8d previous commit
* 62a0ee9 ...

topic/feature still exists in its original form, however, master has a new commit containing everything that topic/feature does. Now, topic/feature can be removed.

cleaning up feature branches

In most cases you want to remove topic/feature after the merge took place, both locally and on the remotes.

Remove local branch:

$ git branch -D topic/feature

Remove remote branch:

$ git push remote :topic/feature

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