Git: Beyond the Basics

gitbeyondthebasics

Thursday, August 2, 12

John Bohn@jjbohn


Developer at OpenSkycurated social commerce


gitwhat is


git is fast and lightweightfree/open sourcedistributedcrazy simple


initbranchaddcommitmerge


Almost any VCS works does this(more or less)

What is special about git?


Interactivity


git add --patchgit add --interactive


Arduino Example


Change Blink


Change Blink

- Two logical changes- Don’t want to bother undoing one- Can’t git add . or git add [file]


git add --patch


git add --patch


git add --patch


git add --patchCommit the change


git add --patchStage other changes

Diff is now empty (everything is staged or commited)Thursday, August 2, 12

git stash


is super boring


until you throw some flags at it...


git stash --no-keep-indexgit stash --keep-index

git stash --patchgit stash --include-untracked

My Favorites


Finding these commands is just a matter of digging


git anything --help


git resetis not

git revert


git reset --soft [sha]git reset --hard [sha]git reset --mixed [sha]


You can also:git reset --patch(but not with those modes)


Bisectingaka: Finding a commit

that screwed things up.


Bisecting


Bisecting

7b35b 912969680d2ab1f c6d43

6 Commits - One BugWe know that 7b35b is goodWe know that cfc332 is badBut we have no idea where the bug was introduced

cfc332


Bisecting

7b35b 912969680d2ab1f c6d43

Tell git what is known good and bad

cfc332good bad


Bisecting

7b35b 912969680d2ab1f c6d43 cfc332good bad


Bisecting

7b35b 912969680d2ab1f c6d43 cfc332good badgood


Bisecting

7b35b 912969680d2ab1f c6d43 cfc332good badgoodgood


Bisecting

7b35b 912969680d2ab1f c6d43 cfc332good badgoodgood

2ab1f is most likely good because the commit after it is


Bisecting

7b35b 912969680d2ab1f c6d43 cfc332good badgoodgood bad


Bisecting

7b35b 912969680d2ab1f c6d43 cfc332good badgoodgood badbad


Recovering lost commits


git reflog


git reflog

Technically shows any action where the tip of a branch is modified

git reflog --allshows stashes, bisects, etc.


Recovery

Let’s say I reset --hard and wiped out the commit that changed my LED to pin 10Use combination of reflog and cherry-pick to get it back


Recovery

Found it! 3ecdba3


RecoveryDouble check that 3ecdba3 is really the commit we want

git diff 3ecdba3^.. 3ecdba3

Shows me the difference between the commit I wantto cherry pick and the commit prior.


git cherry-pickNow cherry pick 3ecdba3 into our working tree

Note: the sha has changed because this commit now hasa different parent than it did when it was recorded into the reflog


RecoveryCheckout the reflog again to see the cherry-pick


Interactive RebasingChanging the past one commit at a time


git rebase -i [commit]








Interactive rebase


git internalsThe plumbing and the porcelain


git internalsgit stores snapshots, not differencesStoring differences is slow and inflexible

CVS/Subversion git


git internalsgit stores snapshots, not differencesStoring differences is slow and inflexible

CVS/Subversion git


git internals

What does a commit look like?


git internals

Let’s investigate a repo

Sorry for the bad “investigation” image ;-)


Thanks!Come work with me at OpenSky!

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Technology

Git: Beyond the Basics