Git Anti-Patterns: How To Mess Up With Git and Love it Again

These are the slides I presented at Devoxx Poland 2017 Conference.

Transcript

1. @lemiorhan #DevoxxPL Platinum Sponsor: GITANTI PATTERNS How To Mess Up With Git and Love It Again LEMi ORHAN ERGiN Agile Software Craftsman, iyzico
2. /lemiorhan lemiorhanergin.com @lemiorhan meetup.scturkey.org agileturkey.org slideshare.net/lemiorhan dev.iyzipay.com LEMi ORHAN ERGiN agile software craftsman @ iyzico agile practice lead at iyzico developing software since 2001 ex-Sony and ex-eBay employee consultant, architect, trainer, developer founder of Software Craftsmanship Turkey ex community leader of Agile Turkey got 1 million+ views for his slides
3. git is powerful but you have to know using it properly
4. Are you using git if all you do is commit-push-pull use dropbox instead ANTIPATTERN DANGER as if it is dropbox ?
5. learn how git works no worries, I will cover how git behaves
6. the way it keeps FILES & FOLDERS working copy staging area objects database repository the way it keeps REFERENCES directed acyclic graph keeping snapshots traversing graph branches, tags, heads git has 2 mechanisms
7. Source Code Working Copy you want to version changes
8. Source Code Working Copy $ git init Object Database .git Folder / Object Database Cache Staging Area / The Index initializing repo
9. Source Code Working Copy $ git init --bare Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server initializing bare repo
10. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git add . preparing commits
11. folder folder folder file file file $ git add . preparing commits
12. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git add . preparing commits
13. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git commit -m “initial commit” commi!ing
14. $ git commit -m “initial commit” commi!ing folder folder folder file file file commit branch HEAD For more details, refer to book Git Internals by Scott Chacon
15. folder folder folder file file file commit $ git commit -m “second commit” commi!ing folder commit branch HEAD folder file folder For more details, refer to book Git Internals by Scott Chacon
16. folder folder folder file file file commit $ git commit -m “third commit” commi!ing folder commit folder file folder folder commit branch HEAD file For more details, refer to book Git Internals by Scott Chacon
17. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git commit -m “initial commit” commi!ing
18. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git remote add origin http://upstream.repo $ git push -u origin master pushing to remote
19. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy new changes from others are pushed
20. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git fetch fetching changes
21. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git merge FETCHED_HEAD updating working copy
22. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git pull git fetch + git merge ge!ing changes to source code
23. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy want to update last commit
24. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git reset --soft $ git commit --amend / so" reseting cannot be reached Only the cache for the commit you reseted is removed from staging area for your current branch
25. folder folder folder file file file commit folder commit folder file folder folder commit branch HEAD file For more details, refer to book Git Internals by Scott Chacon $ git reset --soft $ git commit --amend / so" reseting
26. folder folder folder file file file commit folder commit folder file folder folder commit branch HEAD file For more details, refer to book Git Internals by Scott Chacon $ git reset --soft $ git commit --amend / so" reseting
27. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy want to squash or change last commits
28. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git reset --mixed mixed reseting cannot be reached entries for commits, files and folders are removed from staging area
29. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy want to get rid of last commits
30. Object Database .git Folder / Object Database Cache Staging Area / The Index Remote Upstream Repo / Remote Repo Server Source Code Working Copy $ git reset --hard hard reseting cannot be reached removed from staging area removed from working copy
31. are you brave enough to jump to any commit ? jump to a branch create a branch from a commit create a branch from a tag ANTIPATTERN DANGER $ git checkout feature/PA-121 $ git checkout -b fix/missing-sign-parameter 2449be8 $ git checkout -b hotfix/v1.1 tags/v1
32. are you sure? are you brave enough to jump to any commit ?
33. do you have loooooong living topic branches ? ANTIPATTERN DANGER
34. do you have loooooong living topic branches ? welcome to merge hell
35. before merging do you validate commits back to source ? ANTIPATTERN DANGER code review, continuous integration, automated testing…
36. before merging do you validate commits back to source ? are you sure?
37. merge and unmerge do you o!en want to just before releases ? ANTIPATTERN DANGER
38. merge and unmerge do you o!en want to just before releases ? master HEAD TAG/v13 version 14 $ git cherry-pick Every-Single-Commit-We-Want-To-Deploy
39. the commit graph ? do you fully understand ANTIPATTERN DANGER
40. the commit graph ? do you fully understand topic and shared branches, tracking branches, tags, HEADs, merge commits, reverted commits…
41. Cure?
42. Commit Early, Commit O"en Perfect Later, Publish Once
43. STEP 0 split your big feature into mini shippable tasks master HEAD TOPIC ORIGIN/master refactorings tasks, like rest endpoints testable, deployable each task will have a branch, not a feature
44. STEP 1 commit early commit o!en no need to compile no need for CI it’s only for versioning do not push master HEAD TOPIC ORIGIN/master
45. always pull with rebase $ git pull --rebase origin master to get forced pushes securely to rebase your commits master HEAD TOPIC STEP 2 ORIGIN/master
46. always pull with rebase $ git pull --rebase origin master to get forced pushes securely to rebase your commits master HEAD TOPIC STEP 2 ORIGIN/master
47. always pull with rebase $ git pull --rebase origin master to get forced pushes securely to rebase your commits master HEAD TOPIC STEP 2 ORIGIN/master if you branch is pushed already $ git push -f
48. always pull with rebase $ git pull --rebase origin master to get forced pushes securely to rebase your commits master HEAD TOPIC STEP 2 ORIGIN/master if you branch is pushed already $ git push -f Sync source branch a!erwards $ git fetch origin master:master
49. perfect later make it single commit $ git reset HEAD~3 or $ git rebase -i HEAD~3 HEAD TOPIC STEP 3 ORIGIN/master tests are passing app is working code is reviewed (*) master
50. $ git reset HEAD~3 (then commit) or $ git rebase -i HEAD~3 HEAD TOPIC STEP 3 ORIGIN/master perfect later make it single commit tests are passing app is working code is reviewed (*) master
51. Use feature flags/toggles HEAD TOPIC STEP 4 ORIGIN/master if feature should be disabled merge back to source $ git checkout master $ git merge topic master
52. Use feature flags/toggles master HEAD TOPIC STEP 4 ORIGIN/master if feature should be disabled merge back to source $ git checkout master $ git merge topic
53. Continuous Integration validates master branch continuously master HEAD TOPIC ORIGIN/master Pull requests can be used to review code and to validate before merging back to master Scrum tasks are mapped to commits, not stories Github Flow can be used to govern overall TAMING THE POWER OF GIT make git the king again Feature flags should be used whenever possible Commit early & o"en perfect later, publish once philosophy Deliver frequently be prepared to send every single commit Deleting branches a"er merge will make your commit graph readable
54. Any Other Cures?
55. use terminal GUIs are prison balls of developers it’s ok to use GUIs while checking diffs, resolving conflicts and viewing commit graph
56. do not lose take extra care while using hard reset $ git reset --merge HEAD~ Use stash $ git stash save “updates local settings to keep db safe” $ git reset --hard HEAD~ $ git stash apply stash@{0} Create a new branch $ git checkout -b feature/PA-121 $ git add settings.xml $ git commit -m “adds new settings config” Use hard reset with merge and commit into it uncommited changes
57. TOPIC HEAD MASTER long living branches with care handle Squash all commits in your topic branch and 
 make them available in working copy $ git merge --squash fix Squash commit -- not updating HEAD Automatic merge went well; stopped before committing as requested $ git add . $ git commit -m “adds a feature” $ git branch -D topic
58. long living branches with care handle TOPIC HEAD MASTER $ git merge --squash fix Squash commit -- not updating HEAD Automatic merge went well; stopped before committing as requested $ git add . $ git commit -m “adds a feature” $ git branch -D topic Squash all commits in your topic branch and 
 make them available in working copy
59. stop adding prevent commits from being big ball of muds every change
60. stop adding prevent commits from being big ball of muds every change local change sets at JetBrains IDEs
61. stop adding every change partial add
62. messages are read! # WHAT # <issue id> (this commit will...) <subject> # WHY and HOW # Explain why this change is being made # RELATED # Provide links or keys to any relevant issues or other resources # REMEMBER # use lower case in the subject line # start with a verb in imperative tone in the subject line # do not end the subject line with a period # separate subject from body with a blank line # use the body to explain what and why vs. how # can use multiple lines with "-" for bullet points in body $ git config --global commit.template ~/.git-commit-template.txt $ git config --global commit.cleanup strip .git-commit-template.txt use git commit templates to create be"er commit messages com t m i
63. messages are read! use git commit templates to create be"er commit messages com t m i
64. RECAP what was really happened at that time? LET’S
65. master TAG/v1.1 login HEAD DETACHED HEAD STATE $ git checkout cecd95914 Note: checking out 'cecd95914'. You are in 'detached HEAD' state. You can look around, make experimental changes and commit them, and you can discard any commits you make in this state without impacting any branches by performing another checkout.
66. master TAG/v1.1 login HEAD DETACHED HEAD STATE $ git rebase (and conflicts happen) $ git checkout HEAD~2 $ git checkout 43e3ab01 $ git checkout tags/v1.1 WHEN IT HAPPENS
67. master TAG/v1.1 login HEAD poor little developer...
68. master TAG/v1.1 login HEAD $ git checkout master
69. master TAG/v1.1 login HEAD $ git reflog aa67e3a2c HEAD@{0}: rebase finished: returning to refs/heads/fix/java-sql-Date-violates-LSR aa67e3a2c HEAD@{1}: rebase: fixes UnsupportedOperationException while calling toIstant() method of java.sql.Date a45f3c4e5 HEAD@{2}: rebase: checkout develop 630ddad6e HEAD@{3}: checkout: moving from develop to fix/java-sql-Date-violates-LSR b26cf7a1a HEAD@{4}: rebase: checkout develop 630ddad6e HEAD@{5}: checkout: moving from develop to fix/java-sql-Date-violates-LSR b26cf7a1a HEAD@{6}: pull: Fast-forward 8b59f8f50 HEAD@{7}: checkout: moving from fix/java-sql-Date-violates-LSR to develop
70. $ git reflog 630ddad6e the one we are searching for master TAG/v1.1 login HEAD aa67e3a2c HEAD@{0}: rebase finished: returning to refs/heads/fix/java-sql-Date-violates-LSR aa67e3a2c HEAD@{1}: rebase: fixes UnsupportedOperationException while calling toIstant() method of java.sql.Date a45f3c4e5 HEAD@{2}: rebase: checkout develop 630ddad6e HEAD@{3}: checkout: moving from develop to fix/java-sql-Date-violates-LSR b26cf7a1a HEAD@{4}: rebase: checkout develop 630ddad6e HEAD@{5}: checkout: moving from develop to fix/java-sql-Date-violates-LSR b26cf7a1a HEAD@{6}: pull: Fast-forward 8b59f8f50 HEAD@{7}: checkout: moving from fix/java-sql-Date-violates-LSR to develop
71. master typofix TAG/v1.1 login HEAD $ git branch typofix 630ddad6e
72. master typofix TAG/v1.1 login HEAD $ git branch typofix 630ddad6e KEEP CALM, NOTHING WILL BE LOST
73. LEMi ORHAN ERGiN agile software craftsman @ iyzico /lemiorhan lemiorhanergin.com @lemiorhan DO NOT FORGET VIA MY DEVOXX MOBILE APP TO GIVE FEEDBACK TO LEMI