Debug Code and Rewrite History with Git

A short talk about how to use git bisect, interactive rebase, and git reflog for the first Dev O'Clock HVTech meetup.

Transcript

1. Debug Code and
   Rewrite History
   with Git
   

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2. EILEEN M. UCHITELLE
   Programmer at Basecamp
   ! eileencodes.com
   " @eileencodes
   # @eileencodes
   

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3. Rails Committers Team &
   Rails Security Team
   

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4. PRACTICE REPO
   $ git clone git@github.com:eileencodes/
   railsconf_scripts.git
   $ git checkout practicing-git
   

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5. GIT
   $ git bisect
   $ git rebase -i
   $ git reflog
   

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6. Debugging with
   Git Bisect
   C1 C2 C3 C4 C5 C6 M3 M4
   M0
   

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7. GIT BISECT
   $ git bisect start
   

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8. GIT BISECT
   $ git bisect bad
   $ git bisect good tag-name
   

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9. GIT BISECT
   $ git bisect
   

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10. Rewriting History
    with Git
    C1 C2 C3 C4 C5 C6 M3 M4
    M0
    

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11. Short (50 chars or less) summary of changes
    More detailed explanatory text, if necessary. Wrap it to
    about 72 characters or so. In some contexts, the first
    line is treated as the subject of an email and the rest
    of the text as the body. The blank line separating the
    summary from the body is critical (unless you omit
    the body entirely); tools like rebase can get confused
    if you run the two together.
    Further paragraphs come after blank lines.
    - Bullet points are okay, too
    - Typically a hyphen or asterisk is used for the
    bullet, preceded by a single space, with blank lines in
    between, but conventions vary here
    

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12. Using
    M1 M2 M3 M4
    F1 F2 F1 F2
    M0
    Interactive Rebase
    

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13. GIT
    

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14. GIT REBASE -I
    $ git rebase -i master
    

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15. 1 pick e92e34f Refactor existing code
    2 pick 80601e8 Oops add in missing code
    3 pick 8d91f76 Remove extra piece I left behind
    4 pick 933bd58 Fix bug reported in #9895
    5 pick 99302ef Clean up changes
    6 pick 5cc3c5a Fix spelling mistake in documentation
    7
    8 # Rebase 0131d99..5cc3c5a onto 0131d99
    9 #
    10 # Commands:
    11 # p, pick = use commit
    12 # r, reword = use commit, but edit the commit message
    13 # e, edit = use commit, but stop for amending
    14 # s, squash = use commit, but meld into previous commit
    15 # f, fixup = like "squash", but discard this commit's log
    16 # x, exec = run command (the rest of the line) using shell
    

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16. 1 pick e92e34f Refactor existing code
    2 pick 80601e8 Oops add in missing code
    3 pick 8d91f76 Remove extra piece I left behind
    4 pick 933bd58 Fix bug reported in #9895
    5 pick 99302ef Clean up changes
    6 pick 5cc3c5a Fix spelling mistake in documentation
    7
    8 # Rebase 0131d99..5cc3c5a onto 0131d99
    9 #
    10 # Commands:
    11 # p, pick = use commit
    12 # r, reword = use commit, but edit the commit message
    13 # e, edit = use commit, but stop for amending
    14 # s, squash = use commit, but meld into previous commit
    15 # f, fixup = like "squash", but discard this commit's log
    16 # x, exec = run command (the rest of the line) using shell
    

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17. 1 reword e92e34f Refactor existing code
    2 pick 80601e8 Oops add in missing code
    3 pick 8d91f76 Remove extra piece I left behind
    4 pick 933bd58 Fix bug reported in #9895
    5 pick 99302ef Clean up changes
    6 pick 5cc3c5a Fix spelling mistake in documentation
    7
    8 # Rebase 0131d99..5cc3c5a onto 0131d99
    9 #
    10 # Commands:
    11 # p, pick = use commit
    12 # r, reword = use commit, but edit the commit message
    13 # e, edit = use commit, but stop for amending
    14 # s, squash = use commit, but meld into previous commit
    15 # f, fixup = like "squash", but discard this commit's log
    16 # x, exec = run command (the rest of the line) using shell
    

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18. 1 reword e92e34f Refactor existing code
    2 pick 80601e8 Oops add in missing code
    3 edit 8d91f76 Remove extra piece I left behind
    4 pick 933bd58 Fix bug reported in #9895
    5 pick 99302ef Clean up changes
    6 pick 5cc3c5a Fix spelling mistake in documentation
    7
    8 # Rebase 0131d99..5cc3c5a onto 0131d99
    9 #
    10 # Commands:
    11 # p, pick = use commit
    12 # r, reword = use commit, but edit the commit message
    13 # e, edit = use commit, but stop for amending
    14 # s, squash = use commit, but meld into previous commit
    15 # f, fixup = like "squash", but discard this commit's log
    16 # x, exec = run command (the rest of the line) using shell
    

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19. 1 reword e92e34f Refactor existing code
    2 pick 80601e8 Oops add in missing code
    3 edit 8d91f76 Remove extra piece I left behind
    4 pick 933bd58 Fix bug reported in #9895
    5 squash 99302ef Clean up changes
    6 pick 5cc3c5a Fix spelling mistake in documentation
    7
    8 # Rebase 0131d99..5cc3c5a onto 0131d99
    9 #
    10 # Commands:
    11 # p, pick = use commit
    12 # r, reword = use commit, but edit the commit message
    13 # e, edit = use commit, but stop for amending
    14 # s, squash = use commit, but meld into previous commit
    15 # f, fixup = like "squash", but discard this commit's log
    16 # x, exec = run command (the rest of the line) using shell
    

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20. 1 reword e92e34f Refactor existing code
    2 fixup 80601e8 Oops add in missing code
    3 edit 8d91f76 Remove extra piece I left behind
    4 pick 933bd58 Fix bug reported in #9895
    5 squash 99302ef Clean up changes
    6 pick 5cc3c5a Fix spelling mistake in documentation
    7
    8 # Rebase 0131d99..5cc3c5a onto 0131d99
    9 #
    10 # Commands:
    11 # p, pick = use commit
    12 # r, reword = use commit, but edit the commit message
    13 # e, edit = use commit, but stop for amending
    14 # s, squash = use commit, but meld into previous commit
    15 # f, fixup = like "squash", but discard this commit's log
    16 # x, exec = run command (the rest of the line) using shell
    

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21. 1 reword e92e34f Refactor existing code
    2 fixup 80601e8 Oops add in missing code
    3 edit 8d91f76 Remove extra piece I left behind
    4 pick 933bd58 Fix bug reported in #9895
    5 squash 99302ef Clean up changes
    6 pick 5cc3c5a Fix spelling mistake in documentation
    7
    8 # Rebase 0131d99..5cc3c5a onto 0131d99
    9 #
    10 # Commands:
    11 # p, pick = use commit
    12 # r, reword = use commit, but edit the commit message
    13 # e, edit = use commit, but stop for amending
    14 # s, squash = use commit, but meld into previous commit
    15 # f, fixup = like "squash", but discard this commit's log
    16 # x, exec = run command (the rest of the line) using shell
    

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22. GIT REBASE -I
    $ git rebase -i master
    

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23. 628168
    628168
    50718b
    bc503a1
    C1 C2 C3 C4
    C0
    Git Reflog
    Using
    

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25. GIT REFLOG
    $ git reflog
    

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26. 628c168 HEAD@{0}: rebase -i (finish): returning to refs/heads/your-branch
    628c168 HEAD@{1}: rebase -i (start): checkout master
    628c168 HEAD@{2}: reset: moving to 628c168
    bc503a1 HEAD@{3}: rebase -i (finish): returning to refs/heads/your-branch
    bc503a1 HEAD@{4}: rebase -i (pick): Add Person model and migration
    1ad2ff2 HEAD@{5}: rebase -i (pick): Improve README section on git reflog
    026457d HEAD@{6}: rebase -i (start): checkout master
    633f620 HEAD@{7}: rebase -i (finish): returning to refs/heads/your-branch
    633f620 HEAD@{8}: rebase -i (pick): Improve README section on git reflog
    19f41a7 HEAD@{9}: commit (amend): Add Person model and migration
    50718b1 HEAD@{10}: rebase -i (edit): Add Person model and migration
    026457d HEAD@{11}: rebase -i (reword): Update README with sections on rebase and
    c8c6000 HEAD@{12}: rebase -i (reword): Update README with sections on rebase and
    628fbd2 HEAD@{13}: rebase -i (squash): Update README description section
    455dab0 HEAD@{14}: rebase -i (fixup): # This is a combination of 2 commits.
    4392779 HEAD@{15}: rebase -i (start): checkout master
    628c168 HEAD@{16}: rebase -i (finish): returning to refs/heads/your-branch
    628c168 HEAD@{17}: rebase -i (start): checkout master
    628c168 HEAD@{18}: rebase -i (finish): returning to refs/heads/your-branch
    628c168 HEAD@{19}: rebase -i (start): checkout master
    628c168 HEAD@{20}: rebase: aborting
    1f935f7 HEAD@{21}: rebase -i (edit): Add Person model and migration
    

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27. GIT REFLOG
    $ git reflog
    $ git reset -—hard 628c168
    

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28. EILEEN M. UCHITELLE
    Programmer at Basecamp
    ! eileencodes.com
    " @eileencodes
    # @eileencodes
    Slides:
    speakerdeck.com/eileencodes
    

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