Conflicts

Figure 396. Conflicting changes Slide presentation
User A: Print.java User B: Print.java 
// Driver class
public class Print {
  public static void
    main(String[] args) {
      System.out.println
        (Math.add(2, 3));
  }
}
 
/**
 * Application entry point
 */
public class Print {
  public static void
    main(String[] args) {
      System.out.println
        (Math.add(2, 3));
  }
}

Figure 397. Commit schedule Slide presentation
User A User B
Edit: ... Driver class ... -
git commit, git push -
- edit: ... Application entry point ...
- git commit
- git push: Fail!

Figure 398. User B: git push fails Slide presentation 
>git push ...
To https://gitlab.mi.hdm-stuttgart.de/goik/gitintro.git
 ! [rejected]        master -> master (fetch first)
error: failed to push some refs to
        'https://gitlab.mi.hdm-stuttgart.de/goik/gitintro.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.

Figure 399. User B: git pull fails as well Slide presentation 
>git pull 
...
From https://gitlab.mi.hdm-stuttgart.de/goik/gitintro
   b003a82..dbbedb0  master     -> origin/master
Auto-merging Print.java
CONFLICT (content): Merge conflict in Print.java
Automatic merge failed; fix conflicts and then commit the result.

Figure 400. Merge conflict details Slide presentation 
>git diff Print.java
diff --cc Print.java
index fc36ae6,7b27edf..0000000
--- a/Print.java
+++ b/Print.java
@@@ -1,6 -1,4 +1,10 @@@
++<<<<<<< HEAD
 +/**                        ❶
 + * Application entry point
 + */
++=======
+ // Driver class ❷
++>>>>>>> dbbedb0fc29d77beeaaada37f2538d78f82bac93
public class Print {
  public static void
    main(String[] args) {
      System.out.println
        (Math.add(2, 3));
  }
}

❶

Changes of user A.

❷

Own changes of user B.

Figure 401. Struggling for resolution Slide presentation
Struggling for resolution

Figure 402. Merging Print.java manually Slide presentation 
<<<<<<< HEAD
/**
 * Application entry point 
 */
=======
// Driver class 
>>>>>>> 10cf21c ... 759462c
public class Print {
  public static void
    main(String[] args) {
      System.out.println
        (Math.add(2, 3));
  }
}
 ➱ 
/**
 * Driver class, application entry point 
 */
public class Print {
  public static void
    main(String[] args) {
      System.out.println
        (Math.add(2, 3));
  }
}

Figure 403. Commit and push merge Slide presentation 
>git add Print.java 

>git commit --message "Merging changes" 
[master 173487a] Merging changes

>git push
...
To https://gitlab.mi.hdm-stuttgart.de/goik/gitintro.git
   10cf21c..173487a  master -> master

exercise No. 127

git distributed, DIY

Q:

Find a partner sitting next to you and repeat the current examples from the section called “Shared development with centralized remote.” and most importantly the section called “Conflicts”.

Do not hesitate creating a (source code!) conflict. You'll learn how to resolve it anyway.

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