The Git Historian

Your git repository’s log wants to tell you a story, with valuable clues about how your software became the thing of beauty (or horrible mess) that it is today. You just need to know how and where to look. In this talk, we’ll dig into a project’s history to learn how it evolved, using only the git command line utility to search through commits–no extra software required! To close, we’ll discuss how to leave good clues for future historians.

Transcript

1. The Git Historian
   Aaron Sumner
   

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3. Disclaimers
   • Mileage may vary
   • You probably know something I don’t!
   • Links to slides and references at the end
   

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4. Based on a true story.
   

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5. for development with backup from Webrick"
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6. git blame lib/framework.rb
   

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7. 55a43a7 Fix some stuff
   "
   

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10. #
    

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11. commit
    55a43a73b1f7be5f410f81e58ec1df24a1792bd5
    Author: Aaron Sumner
    Date: Mon Mar 20 19:32:25 2017 -0500
    Fix some stuff
    $
    

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12. What went wrong?
    

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13. %
    %
    

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14. %
    

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15. What’s the story?
    

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16. The Git Historian
    &
    '
    

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17. Digging through
    history '
    

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18. thoughtbot/clearance
    

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19. git blame file
    git show SHA
    

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25. git log
    

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44. Useful flags for git log
    git log --reverse
    git log --oneline
    git log --patch (-p)
    git log -p path/to/file
    git log -p -S term
    git log --grep term
    git log --stat
    man git-log
    

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45. Pager (less -S)
    

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54. Searching git log
    /pattern
    ?pattern
    n for next instance
    N for previous instance
    j/k one line down/up
    gg beginning of output
    G end of output
    /^commit
    man less
    

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55. Leaving a trail
    &
    

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56. Atomic commits
    

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57. git add -am “fix it”
    %
    

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58. git add -p
    git commit
    (
    

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66. Tips for a clean commit
    • Include the code, corresponding documentation,
    and corresponding test coverage
    • Separate out refactoring that could obfuscate the
    feature change
    • Keep other corrections in separate commits
    

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67. “The seven rules of a great
    commit message”
    1. Separate subject from body with a blank line
    2. Limit the subject line to 50 characters
    3. Capitalize the subject line
    4. Do not end the subject line with a period
    5. Use the imperative mood in the subject line
    6. Wrap the body at 72 characters
    7. Use the body to explain what and why vs. how
    

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68. Rebasing
    

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69. ☠
    

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70. git rebase commit
    git rebase branch
    git rebase tag
    

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71. git rebase --interactive
    commit
    

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72. git rebase --interactive
    --autosquash commit
    

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98. git rebase --interactive
    --autosquash
    git commit --fixup sha
    git commit --squash sha -m “Additional
    information.”
    

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99. Summary
    

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100. ' git blame
     git show
     git log
     

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101. git add -p
     git rebase
     good messages!
     &
     

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102. speakerdeck.com/ruralocity
     www.aaronsumner.com
     

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103. References
     • https://everydayrails.com/2017/01/02/git-command-line-log-search.html
     • http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html
     • https://chris.beams.io/posts/git-commit/
     • http://johnkary.net/blog/git-add-p-the-most-powerful-git-feature-youre-not-
     using-yet/
     • https://technosorcery.net/blog/2010/02/fun-with-the-upcoming-1-7-release-of-
     git-rebase-interactive-autosquash/
     • https://github.com/rkh/almost-sinatra
     • https://github.com/thoughtbot/clearance
     • http://emojipedia.org/
     

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