Merge like it's 2099 (AndroidMakers 2017)

Every developer working in a team of more than 2 person has experienced conflicts when merging, rebasing or cherry picking a commit. Resolving those conflicts is a tedious task and it's time for a change. This talk will propose a solution to merge smarter and not harder.

Transcript

1. Merging like it’s 2099 ! Introducing the AutoMergeTool Android Makers 2017 - Paris
2. About... Xavier F. Gouchet Android Architect Jenkins/Sonar Admin Bash/Python dev tools Bad Puns Advocate @xgouchet on Github, StackOverflow, Twitter, …
3. “ “Put your hands in the air” Placebo @xgouchet
4. Git @xgouchet
5. Git Merge @xgouchet
6. Conflicts @xgouchet
7. “ “Let’s start at the very begining (a very good place to start)” Julie Andrews @xgouchet
8. @xgouchet Our first commit commit 1e7dfd3e0c6715f3e611975892d8618afb7c33a6 Author: _alex <_alex@...> Date: Tue Jan 6 14:56:57 2009 +0000 Created folder git-svn-id: file:///opt/svn-android/trunk@2 966f65aa-2a5b-49e2-8ec6-7a0f9cdf547d
9. Our code base ◎ 8 years ◎ 12’000+ commits ◎ 30+ different committers ◎ 750’000+ lines of code* ◎ 200’000+ lines of comments* ◎ 7’500+ source files* * Java, XML, python, gradle, shell @xgouchet
10. “ “Too many problems, oh why am I here?” Megadeth @xgouchet
11. CVS is text based @xgouchet
12. Text based ? ◎ Diff / Merge is based on a stream of characters. ◎ Easy (and fast-ish) to compute ◎ Recognizes newlines / whitespace ◎ Doesn’t understand any syntax¹ @xgouchet
13. Common conflicts ◎ The imports section ◎ Same change on both sides ◎ Additions at the same place ◎ Changes in different lines in same block ◎ Unrelated changes on same line ◎ … ? @xgouchet
14. “ “Most of those are easy, but tedious to solve” @xgouchet
15. “ “There must be a better way to make the things we want…” Paul Mc Cartney @xgouchet
16. Smarter merge tool @xgouchet
17. Basic principle ◎ Many simple automatic solvers ◎ Language agnostic ◎ Manual solving as a “last resort” solution ◎ Integrate with git / 3rd party tools @xgouchet
18. $ git rebase develop $ git mergetool Auto Merge Tool Process auto auto auto @xgouchet
19. $ git merge feature/foo $ git mergetool auto auto auto Auto Merge Tool Process @xgouchet
20. Configuration (~/.gitconfig) [merge] tool = amt [mergetool "amt"] cmd = amt.py -l $LOCAL -r $REMOTE -b $BASE -m $MERGED [amt] tools = java_imports;gen_additions;custom;meld [mergetool "java_imports"] order = android [mergetool "custom"] cmd = custom.sh "$LOCAL" "$REMOTE" "$MERGED" extensions = html;xml @xgouchet
21. Configuration (~/.gitconfig) [merge] tool = amt [mergetool "amt"] cmd = amt.py -l $LOCAL -r $REMOTE -b $BASE -m $MERGED [amt] tools = java_imports;gen_additions;custom;meld [mergetool "java_imports"] order = android [mergetool "custom"] cmd = custom.sh "$LOCAL" "$REMOTE" "$MERGED" extensions = html;xml @xgouchet
22. Configuration (~/.gitconfig) [merge] tool = amt [mergetool "amt"] cmd = amt.py -l $LOCAL -r $REMOTE -b $BASE -m $MERGED [amt] tools = java_imports;gen_additions;custom;meld [mergetool "java_imports"] order = android [mergetool "custom"] cmd = custom.sh "$LOCAL" "$REMOTE" "$MERGED" extensions = html;xml @xgouchet
23. Configuration (~/.gitconfig) [merge] tool = amt [mergetool "amt"] cmd = amt.py -l $LOCAL -r $REMOTE -b $BASE -m $MERGED [amt] tools = java_imports;gen_additions;custom;meld [mergetool "java_imports"] order = android [mergetool "custom"] cmd = custom.sh "$LOCAL" "$REMOTE" "$MERGED" extensions = html;xml @xgouchet
24. Configuration (~/.gitconfig) [merge] tool = amt [mergetool "amt"] cmd = amt.py -l $LOCAL -r $REMOTE -b $BASE -m $MERGED [amt] tools = java_imports;gen_additions;custom;meld [mergetool "java_imports"] order = android [mergetool "custom"] cmd = custom.sh "$LOCAL" "$REMOTE" "$MERGED" extensions = html;xml @xgouchet
25. Configuration (~/.gitconfig) [merge] tool = amt [mergetool "amt"] cmd = amt.py -l $LOCAL -r $REMOTE -b $BASE -m $MERGED [amt] tools = java_imports;gen_additions;custom;meld [mergetool "java_imports"] order = android [mergetool "custom"] cmd = custom.sh "$LOCAL" "$REMOTE" "$MERGED" extensions = html;xml @xgouchet
26. Automatic conflict solvers ◎ Language agnostic ◦ Addition at the same line ◦ Deleting the same block ◦ Woven conflicts ◦ … ◎ Language specific ◦ Java Imports ◦ … @xgouchet
27. Early results @xgouchet
28. Specific Case ◎ Rebased a huuuuge commit (+1537, -3250) ◎ Number of conflicted files : 37 ◎ Number of conflicts : 62 ◎ Number of conflicts solved manually : 3 ◎ Time spent : 2 minutes* * plus time to write AutoMergeTool @xgouchet
29. Globally ◎ Used since december 2016 ◎ Number of manual conflicts down by 75% ◎ Mood increased by 100% @xgouchet
30. http://www.github.com/xgouchet/AutoMergeTool Going further @xgouchet
31. ◎ Semantic Merge ($6.90/month) ◎ DeltaXML (XML only) ◎ Why doesn’t this exist yet: Syntax-aware merge ¹ Going even further @xgouchet
32. Thanks! Any questions? http://www.github.com/xgouchet/AutoMergeTool @xgouchet