Git risky using git metadata to predict code bug risk
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The document presents a framework for predicting code bug risk using Git metadata by building a model based on the history of commits. It outlines steps for identifying bug-inducing commits, constructing features, training a binary classifier, and implementing Git hooks to score new commits. Emphasis is placed on the importance of good commit hygiene for effective outcomes in bug tracking and classification.
Git risky using git metadata to predict code bug risk
- 1. using git metadata to predict code bug risk git risky
- 3. Outline 1. intro to git 2. the model 3. git tips
- 4. intro to git & git metadata
- 5. 5Civis Analytics | Proprietary and Confidential what is git? 1. a version control tool
- 6. 6Civis Analytics | Proprietary and Confidential what is git? 1. a version control tool 2. a source of interesting metadata about the history of your codebase
- 7. 7Civis Analytics | Proprietary and Confidential what is a git commit? git records changes to your code in units called ‘commits’. ● a single commit can contain changes to multiple files ● each commit gets assigned a unique identifier ● each commit also has metadata attached to it.
- 8. 8Civis Analytics | Proprietary and Confidential getting at git metadata three git commands are particularly useful for extracting git metadata: ● git log shows the history of changes to a project. different arguments expose different data, e.g. ○ the commit message ○ which files and lines were changed ○ who made the change
- 9. 9Civis Analytics | Proprietary and Confidential three git commands are particularly useful for extracting git metadata: ● git log shows the history of changes to a project. different arguments expose different data, e.g. getting at git metadata
- 10. 10Civis Analytics | Proprietary and Confidential three git commands are particularly useful for extracting git metadata: ● git log shows the history of changes to a project. different arguments expose different data, e.g. getting at git metadata
- 11. 11Civis Analytics | Proprietary and Confidential getting at git metadata three git commands are particularly useful for extracting git metadata: ● git diff shows the changes between two commits
- 12. 12Civis Analytics | Proprietary and Confidential getting at git metadata three git commands are particularly useful for extracting git metadata: ● git blame identifies the last commit to modify a particular line of code codecommit
- 13. building a code bug risk model
- 14. 14Civis Analytics | Proprietary and Confidential build a model of code bug risk! 1. identify and label commits which introduced bugs 2. build commit-level features 3. train a binary classifier on the features and labels 4. score each new commit with the model using git hooks what can you do with git metadata?
- 15. 15Civis Analytics | Proprietary and Confidential step 1: identify commits which introduced bugs ● find commits which fix a bug by checking for commit messages which start with ‘BUG’ or ‘Fix’ ● identify the lines which were changed in that commit using git diff ● find the last commit to modify those lines using git blame ● label that commit as having introduced a bug
- 16. 16Civis Analytics | Proprietary and Confidential step 1: identify commits which introduced bugs caveat: this depends heavily on having good ‘commit hygiene’ ● each commit should only do one thing ● commit messages should be meaningful and standardized at the end we’ll go over some tips for better commit hygiene
- 17. 17Civis Analytics | Proprietary and Confidential step 1: identify commits which introduced bugs ● find commits which fix a bug by checking for commit messages which start with ‘BUG’ or ‘Fix’ git log -i --grep='bug' --grep='fix' --pretty=oneline --abbrev-commit
- 18. 18Civis Analytics | Proprietary and Confidential step 1: identify commits which introduced bugs ● identify the lines which were changed in that commit using git diff git diff <commit hash>^ <commit hash> -U0
- 19. 19Civis Analytics | Proprietary and Confidential step 1: identify commits which introduced bugs ● find the last commit to modify those lines using git blame git blame <file path> <commit hash>^ -L<start line #>,<stop line #> after before
- 20. 20Civis Analytics | Proprietary and Confidential step 1: identify commits which introduced bugs ● label that commit as having introduced a bug with a little python string parsing and some subprocess.check_output calls we can repeat this process for each bugfix commit, and so label all commits by whether or not they introduced a bug.
- 21. 21Civis Analytics | Proprietary and Confidential step 2: build commit-level features if we want to build a model we need features and labels. we just made some labels, so next let’s make some features. git log --stat
- 22. 22Civis Analytics | Proprietary and Confidential step 2: build commit-level features if we want to build a model we need features and labels. we just made some labels, so next let’s make some features. git log --stat
- 23. 23Civis Analytics | Proprietary and Confidential step 2: build commit-level features if we want to build a model we need features and labels. we just made some labels, so next let’s make some features. git log --stat
- 24. 24Civis Analytics | Proprietary and Confidential step 3: train a binary classifier on the features and labels AUC = 0.76
- 25. 25Civis Analytics | Proprietary and Confidential step 3: train a binary classifier on the features and labels
- 26. 26Civis Analytics | Proprietary and Confidential step 3: train a binary classifier on the features and labels again, this really requires good ‘commit hygiene’ ● each commit should only do one thing ● commit messages should be meaningful and standardized
- 27. 27Civis Analytics | Proprietary and Confidential step 4: score each new commit with the model using git hooks git hooks are small scripts in <your repo>/.git/hooks/ that run automatically based on certain git actions. some available hooks are: ● pre-commit ● commit-msg ● post-commit
- 28. 28Civis Analytics | Proprietary and Confidential for model scoring we want the post-commit hook step 4: score each new commit with the model using git hooks <repo>/.git/hooks/post-commit
- 29. 29Civis Analytics | Proprietary and Confidential step 4: score each new commit with the model using git hooks
- 30. tips for better commit hygiene
- 31. 31Civis Analytics | Proprietary and Confidential why care about commit hygiene? ● clean commit histories can help you understand the evolution of the codebase at a glance. ● it adds ‘documentation’ to every line of code: to understand some confusing lines read the commit messages of the commits which added those lines. ● it’s not that hard.
- 32. 32Civis Analytics | Proprietary and Confidential improving git commit messages use the commit-msg hook to ● reject commit messages that are too short ● enforce standards around message tags (eg BUG, TST, WIP, etc)
- 33. 33Civis Analytics | Proprietary and Confidential what if I already made lots of edits to one file? git add --patch <file> if you’ve made lots of edits to a single file you can split those edits into separate commits with the --patch option
- 34. 34Civis Analytics | Proprietary and Confidential what if I already have a messy commit history? git rebase -i <base commit hash> interactive rebasing lets you rewrite your commit history: you can combine, split, reorder, and reword commits
- 35. 35Civis Analytics | Proprietary and Confidential what if I already have a messy commit history? git rebase -i <base commit hash> with rebase -i it is super easy to make tons of small commits as you work and then quickly combine them into a clean commit history. warning: only rebase code you haven’t shared with anyone yet. <base commit hash> should be the most recent commit that other people can see (eg the upstream master).
- 36. questions?