Reverting a merge. Without console. Mikhail Matrosov, Align Technology, CEE-SECR 2017

If you are a little frustrated with what “reverting a merge” is, this talk is for you. Using this operation as an example, I will talk about some important yet non-obvious Git concepts, which we need in our daily work. Notably, I am not going to show a single console command, rather using client with graphical interface to perform all operations. The basic knowledge of Git is assumed.

Transcript

1. October 2017, St. Petersburg Software Engineering Conference Russia Reverting a merge Mikhail Matrosov Technical Manager at Align Technology
4. 4 
5. 5  ^
6. 6  ^ !..
7. 7  ^ ?..
8. Header Hash Changeset 8 master Parents 1 – regular >1 – merge 0 – root
9. A B C D E M master dev 9
10. A B C D E M master 10 1 2 1 = merged to 2 = merged from
11. A B C D E M’ master dev 11 2 1
12. 12 A B C D E M master 1 2 A B C D E M’ master 2 1
15. A B C D E master 15 M ^M F M2 dev only F is merged
16. A B C D E master 16 M ^M F ^^M dev F is merged, D and E brought back by ^^M M2 Pros: commits D and E are preserved Cons: complicated history
17. A B C D E master 17 M ^M dev D’ E’ F M2 Pros: new branch has regular workflow Cons: commits D and E are duplicated
18. A B C D E master 18 M ^M dev ^^M F M2 Pros: preserves conflicts resolution happened in M Cons: commits D and E are not visible in new branch
20. A B C D E M master dev 20
21. Resetting the merge • When you immediately realize the problem • --force-with-lease 21
24. References • Basic info: https://git- scm.com/blog/2010/03/02/undoing-merges.html • More details: https://opensource.apple.com/source/Git/Git- 26/src/git-htmldocs/howto/revert-a-faulty- merge.txt • On order of commits: http://devblog.nestoria.com/post/98892582763/ maintaining-a-consistent-linear-history-for-git 24