Exercises - Branches, merges, and conflicts¶

In order to do these exercises, you need to download the exercises zip file (if you already did so for the previous exercise, you do not need to do so again, of course).

You can do that either by cloning the repository or by just getting the zip file with wget.

• Do ONE of the following:
  • git clone
    1. git clone https://github.com/hpc2n/course-intro-git.git
    2. cd course-intro-git
    3. unzip git_materials.zip
    4. cd git_materials
    5. cd 5.branches
  • Fetch with wget
    1. wget https://github.com/hpc2n/course-intro-git/raw/refs/heads/main/git_materials.zip
    2. unzip git_materials.zip
    3. cd git_materials
    4. cd 5.branches

You are now in a directory with 5 subdirectories, one for each exercise.

1. Merging two local branches¶

Start by making sure you are in the directory git_materials/5.branches/1.merge-ok/recipes.

1. First do git status to look at the status. You can also run git log so you can compare before and after merging.
2. Now try to merge the two branches. You will see that it merges with a “fast-forward” merge.
   NOTE: Remember to check that you are on the right branch! Use git branch to check.
   Merging the branch “fixed-recipe” to the “master” branch:

   git merge fixed-recipe
   

   
   
3. See that the merge goes well, and that git reports using “fast-forward” merge.
   
4. Do git log and git status after the merge and compare what you got before.
   
5. Think about why git could merge the two braches automatically and why it used “fast-forward” merge.

2. Merging two local branches, recursive¶

Start by making sure you are in the directory git_materials/5.branches/2.merge-ok-recursive/recipes.

1. First do git status to look at the status. Also run git log and see the commits that have been made and to which branches.
   
2. Now try to merge the two branches. You will see that the merge happens with “recursive” merge.
   NOTE: Remember to check you are on the right branch before you try to merge!
   Merge the branch “fixed-recipe” to the “master” branch using the git mergecommand.
   
3. Notice that the merge goes well and that git reports using “recursive” merge.
   
4. Do git logand git status after the merge and compare with what you got before.
   
5. Why did git use “recursive” merge?

3. Merging two local branches resulting in a merge conflict¶

Start by making sure you are in the directory git_materials/5.branches/3.merge-bad/recipes.

1. Do a git statusfirst and note the result. Run git log. You could also look at the output from the longer command:
   
   

   $ git log --oneline --abbrev-commit --all --graph
   

   or with the alias command git graph
   NOTE: Remember to change to the subdirectory “recipes” first!
   
2. Now try to merge the two branches with the git merge command and see that a conflict happens.
   NOTE: Check with git branch to find out if you are on the right branch before trying to merge.
   You will get an error similar to this:
   

   $ git merge metric
   Auto-merging cakerecipe.txt
   CONFLICT (content): Merge conflict in cakerecipe.txt
   Automatic merge failed; fix conflicts and then commit the result.
   

   
   
3. Use git log (including with the above mentioned flags) and git status to see where the problems are and see if you can fix the conflict and then reattempt the merge.

4. Rebase two local branches¶

Start by making sure you are in the directory git_materials/5.branches/4.rebase-ok/recipes.

1. First do a git status and a git log and look at the results. Also look at the output at the longer command (git graph):
   

   $ git log --oneline --abbrev-commit --all --graph
   

   
   And save the result somewhere for later comparison.
   
2. Now try to rebase the “master” with the new branch, “fixed-recipe”. You will see that the rebase succeeds.
   
   NOTE: Remember to check with git branch that you are on the right branch before you try to rebase!
   
3. You should now validate the operation with git log and git status.
   Also run git graph or git log with the following flags:
   
   

   $ git log --oneline --abbrev-commit --all --graph
   

5. Rebase two local branches resulting in a conflict¶

Start by making sure you are in the directory git_materials/5.branches/5.rebase-bad/recipes.

1. Check status and history with git status and git graph or git log first, including with the following flags to git log:

$ git log --oneline --abbrev-commit --all --graph

NOTE: Remember to check with git branch to find out if you are on the right branch before trying to rebase.

You will get an error more or less similar to this:

$ git rebase master
First, rewinding head to replay your work on top of it...
Applying: Change from imperial units to metric units.
Using index info to reconstruct a base tree...
M        cakerecipe.txt
Falling back to patching base and 3-way merge...
Auto-merging cakerecipe.txt
CONFLICT (content): Merge conflict in cakerecipe.txt
error: Failed to merge in the changes.
Patch failed at 0001 Change from imperial units to metric units.
Use 'git am --show-current-patch' to see the failed patch

Resolve all conflicts manually, mark them as resolved with
"git add/rm <conflicted_files>", then run "git rebase --continue".
You can instead skip this commit: run "git rebase --skip".
To abort and get back to the state before "git rebase", run "git rebase --abort".