Gitting More Out Of Git

Gitting More Out of Git

Jordan Kasper | @jakerella

Danger!

Git is Distributed

A centralized VCS

https://docs.joomla.org/Dvcs

A distributued VCS

https://docs.joomla.org/Dvcs

A distributued VCS (in practice)

https://docs.joomla.org/Dvcs

Remotes

Just like it sounds, a "remote" is a repo outside your environment.

Cloning

~$ git clone http://some.repo.com someDirectory


~$ git branch -a
* master
  remotes/origin/master

Cloning creates a remote called "origin"

Tracking

A local branch may "track" a remote URL...


~$ git branch -vv
* master             b956c45 [origin/master] Initial commit
  some-local-branch  a74b295 Implemented that cool feature

Wherezitat?


~$ git remote -v
origin  https://github.com/jakerella/repo-name.git (fetch)
origin  https://github.com/jakerella/repo-name.git (push)

Tracking

How do I make a new branch "track" that remote repo?


~$ git checkout -b new-feature
~$ git branch --set-upstream-to=origin/new-feature


~$ git branch -u origin/new-feature


~$ git push -u origin new-feature


~$ git branch -vv
  master            b956c45 [origin/master] Initial commit
* new-feature       b956c45 [origin/new-feature] Initial commit
  some-local-branch a74b295 Implemented that cool feature

Other remotes

What about other repos? How is this distributed?


~$ git remote add jquery-source https://github.com/jquery/jquery.git


~$ git remote -v
origin         https://github.com/jakerella/jquery.git (fetch)
origin         https://github.com/jakerella/jquery.git (push)
jquery-source  https://github.com/jquery/jquery.git (fetch)
jquery-source  https://github.com/jquery/jquery.git (push)


~$ git fetch jquery-source
...
~$ git merge jquery-source/master

Branch Differences


~$ git diff master stuff


diff --git a/README.md b/README.md
index a1e4bac..e69de29 100644
--- a/README.md
+++ b/README.md
@@ -1 +0,0 @@
-This is the readme
diff --git a/STUFF.md b/STUFF.md
new file mode 100644
index 0000000..e69de29

Branch Differences


~$ git diff master stuff

This is ALL changes between master and stuff

(regardless of what branch those came from).

Single-Branch Differences


~$ git diff master...stuff
diff --git a/STUFF.md b/STUFF.md
new file mode 100644
index 0000000..e69de29

Single-Branch Differences


~$ git diff b9bdb02 b86e65d
diff --git a/STUFF.md b/STUFF.md
new file mode 100644
index 0000000..e69de29

Git and Data Integrity

Git uses snapshots

(versus file diffs)

File Diffs

http://git-scm.com/book/en/Getting-Started-Git-Basics

Snapshots

http://git-scm.com/book/en/Getting-Started-Git-Basics

Commit Hashes


~$ git commit -m "Added documentation"
[master (root-commit) b9bdb02] Added documentation


~$ git log
commit b9bdb0261ee9bcaa31d7eb062c0bcafee3e530f0
Author: jdoe <john@doe.com>
Date:   Fri Jul 11 17:27:14 2014 -0500

Added documentation

When things go wrong...

Fixing commit messages


~$ git commit -m "This is teh best."
[feature-branch fd0091e] This is teh best.
1 file changed, 1 insertion(+)


~$ git commit --amend -m "This is the best."
[feature-branch 0486a7d] This is the best.
1 file changed, 1 insertion(+)

Fixing commit messages


~$ git commit -m "This is teh best."
[feature-branch fd0091e] This is teh best.
1 file changed, 1 insertion(+)


~$ git commit --amend -m "This is the best."
[feature-branch 0486a7d] This is the best.
1 file changed, 1 insertion(+)

What about the log?


~$ git log
commit 0486a7d61ee9bcaa31d7eb062c0bcafee3e530f0
Author: jdoe <john@doe.com>
Date:   Fri Jul 11 17:27:14 2014 -0500

This is the best.

commit 72267fc26d88fa977d24760252da63b46ca3b81a
Author: fbar <foo@bar.com>
Date:   Fri Jul 10 14:31:36 2014 -0500

I did a thing!

Never really gone...


~$ git reflog
0486a7d HEAD@{0}: commit (amend): This is the best.
fd0091e HEAD@{1}: commit: This is teh best.
72267fc HEAD@{2}: commit: I did a thing!
...

What if I forgot a file?


~$ git add forgotten.js
~$ git commit --amend

And what if I need to modify an older commit?

You'll need to use git rebase --interactive

Interactive Rebasing


~$ git rebase --interactive HEAD^^^


pick 7e10e41 some old commit
pick 72267fc I did a thing!
pick fd0091e This is the best.

# Rebase 5a39902..fd0091e onto 5a39902 (3 command(s))
#
# Commands:
#  p, pick = use commit
#  r, reword = use commit, but edit the commit message
#  e, edit = use commit, but stop for amending
#  s, squash = use commit, but meld into previous commit
#  f, fixup = like "squash", but discard this commit's log message
#  x, exec = run command (the rest of the line) using shell
...

Interactive Rebasing


~$ git rebase --interactive HEAD^^^


pick 7e10e41 some old commit
edit 72267fc I did a thing!
pick fd0091e This is the best.

# Rebase 5a39902..fd0091e onto 5a39902 (3 command(s))
#
# Commands:
#  p, pick = use commit
#  r, reword = use commit, but edit the commit message
#  e, edit = use commit, but stop for amending
#  s, squash = use commit, but meld into previous commit
#  f, fixup = like "squash", but discard this commit's log message
#  x, exec = run command (the rest of the line) using shell
...


~$ git rebase --interactive HEAD^^^
Stopped at 72267fc26d88fa977d24760252da63b46ca3b81a... I did a thing!
...

Now alter the commit just like before...


~$ git add forgotten-file.js
~$ git commit --amend
...
~$ git rebase --continue
Successfully rebased and updated refs/heads/new-feature.

Careful! You've just changed
ALL history from that point forward.


~$ git reflog

5e83670 HEAD@{0}: rebase -i (finish): returning to refs/heads/new-feature
5e83670 HEAD@{1}: rebase -i (pick): This is the best
bcb51f9 HEAD@{2}: commit (amend): I did a thing!
72267fc HEAD@{3}: cherry-pick: fast-forward
7e10e41 HEAD@{4}: rebase -i (start): checkout HEAD^^^
fd0091e HEAD@{9}: commit: This is the best
72267fc HEAD@{10}: commit: I did a thing!
7e10e41 HEAD@{11}: commit: some old commit

Undoing Changes

Unstaged Changes


~$ echo "foobar" >> README.md


~$ git status
# On branch new-feature
# Changes not staged for commit:
#   (use "git add <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#    modified:   README.md

Unstaged Changes


~$ git checkout README.md

~$ git status
# On branch new-feature
nothing to commit (working directory clean)

You can also `checkout` entire directories:


~$ git checkout src/js/

Unstaged Changes

Be careful! NEW files will not be removed!


~$ git checkout src/js/
~$ git status
On branch master

Untracked files:
  (use "git add <file>..." to include in what will be committed)

       	src/js/foobar.js


~$ rm src/js/foobar.js

Staged Changes


~$ echo "foobar" >> README.md
~$ git add README.md


~$ git status
# On branch new-feature
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   modified:   README.md

Staged Changes


~$ git reset HEAD README.md


~$ git status
# On branch new-feature
# Changes not staged for commit:
#   (use "git add <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#   modified:   README.md

`HEAD` is just a reference to the commit
at the end of the current branch!

So what is "staging" and "working directory"?

Remember the Three States!

Undoing Committed Changes

(a.k.a. Oops)

Bad Commit


~$ echo "foobar" >> README.md

~$ git add README.md
~$ git commit -m "this is not a good change"


~$ git log
commit d42c38661ee9bcaa31d7eb062c0bcafee3e530f0
Author: jdoe <john@doe.com>
Date:   Fri Jul 11 17:27:14 2014 -0500

this is not a good change

Using `reset`

Understanding the Three Seashells

Understanding the Three Seashells

git reset --soft HEAD^

Soft Reset


~$ git reset --soft HEAD^

~$ git log
commit b86e65dab535623d487e063ef1337cfdecfaf99d
Author: jdoe <john@doe.com>
Date:   Fri Jul 10 12:45:11 2014 -0500

the immediately previous change (totally normal)


~$ git status
# On branch new-feature
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#    modified:   README.md

git reset --mixed HEAD^

Mixed Reset


~$ git reset --mixed HEAD^

~$ git log
commit b86e65dab535623d487e063ef1337cfdecfaf99d
Author: jdoe <john@doe.com>
Date:   Fri Jul 10 12:45:11 2014 -0500

the immediately previous change (totally normal)


~$ git status
# On branch new-feature
# Changes not staged for commit:
#   (use "git add <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#   modified:   README.md

git reset --hard HEAD^

Hard Reset


~$ git reset --hard HEAD^

~$ git log
commit b86e65dab535623d487e063ef1337cfdecfaf99d
Author: jdoe <john@doe.com>
Date:   Fri Jul 10 12:45:11 2014 -0500

the immediately previous change (totally normal)

~$ git status
# On branch new-feature
nothing to commit (working directory clean)

Oh no!

I reset --hard and lost some work...

Understanding the reflog


~$ git reflog

b86e65d HEAD@{0}: reset: moving to HEAD^
d42c386 HEAD@{1}: commit: this is not a good change
b86e65d HEAD@{2}: commit: the immediately previous change (totally normal)
e098369 HEAD@{3}: checkout: moving from master to new-feature
b9bdb02 HEAD@{4}: commit: a really good change
e098369 HEAD@{5}: pull: Fast-forward

Understanding the reflog


~$ git reset --hard HEAD@{1}


~$ git reflog

d42c386 HEAD@{0}: reset: moving to HEAD@{1}
b86e65d HEAD@{1}: reset: moving to HEAD^
d42c386 HEAD@{2}: commit: this is not a good change
b86e65d HEAD@{3}: commit: the immediately previous change (totally normal)
e098369 HEAD@{4}: checkout: moving from master to new-feature
b9bdb02 HEAD@{5}: commit: a really good change
e098369 HEAD@{6}: pull: Fast-forward


~$ git log --oneline
d42c386 this is not a good change
b86e65d the immediately previous change (totally normal)
b9bdb02 a really good change

HEAD notation

HEAD^ (back one place from current HEAD)
HEAD^^ (back two places from current HEAD)
HEAD~n (back 'n' places from current HEAD)
HEAD@{i} (back to reflog index 'i')

My boss just told me to pivot...

Using git stash

The Situation

You've made some changes on a feature branch, but they are not ready to commit yet...


~$ git checkout -b hot-fix-123


~$ git status
On branch hot-fix-123
Changes not staged for commit:
    ...
    modified:   borked-code.js
    modified:   some-unrelated-file.js

Untracked files:
    ...
    new-code.js

Using the Stash


~$ git stash --include-untracked
Saved working directory and index state WIP on new-feature: 3c927dd Added text to readme
HEAD is now at 3c927dd Added text to readme


~$ git status
# On branch new-feature
nothing to commit (working directory clean)

Managing Your Stash


~$ git stash list
stash@{0}: WIP on new-feature: 3c927dd Added text to readme

But what if you stash multiple times?!


~$ git stash list
stash@{0}: WIP on new-feature: 3c927dd Added text to readme
stash@{1}: WIP on new-feature: 3c927dd Added text to readme
stash@{2}: WIP on new-feature: 3c927dd Added text to readme
stash@{3}: WIP on hot-fix-456: a46c33b Replaced old lib with new one

Naming Your Stash


~$ git stash save 'work on the API for new feature'

~$ git stash list
stash@{0}: On new-feature: work on the API for new feature
stash@{1}: On new-feature: trying out some async behavior
stash@{2}: On hot-fix-456: attempt to fix bug #456, but incomplete

Great, but how do I use it?

Applying Your Stash


~$ git stash apply


On branch new-feature
Changes not staged for commit:
    ...
    modified:   borked-code.js
    modified:   some-unrelated-file.js

Untracked files:
    ...
    new-code.js


~$ git stash list
stash@{0}: On new-feature: work on the API for new feature
stash@{1}: On new-feature: trying out some async behavior
stash@{2}: On hot-fix-456: attempt to fix bug #456, but incomplete

Dropping Your Stash


~$ git stash drop stash@{0}
Dropped refs/stash@{0} (a52d9c3ba1121dd94eb3925ba60d3f8ef30540c8)

Make sure you know which stash you're dropping!

Popping Your Stash


~$ git stash pop


On branch new-feature
Changes not staged for commit:
    ...
    modified:   borked-code.js
    modified:   some-unrelated-file.js

Untracked files:
    ...
    new-code.js

Dropped refs/stash@{0} (a52d9c3ba1121dd94eb3925ba60d3f8ef30540c8)


~$ git stash list
stash@{0}: On new-feature: trying out some async behavior
stash@{1}: On hot-fix-456: attempt to fix bug #456, but incomplete

Logs

http://thedailyomnivore.net/2012/02/20/ren-stimpy/

The Basic Log


~$ git log
commit d42c38691161f42fcc07d806f7df4579e8cd189e
Author: jakerella <jordan@jordankasper.com>
Date:   Sat Jul 5 15:57:36 2014 -0500

Added text to readme

commit b9bdb0261ee9bcaa31d7eb062c0bcafee3e530f0
Author: jakerella <jordan@jordankasper.com>
Date:   Sat Jul 5 15:36:30 2014 -0500

Added documentation
...

Log Options


~$ git log --oneline

d42c386 Added text to readme
b9bdb02 Added documentation
c2cb87e removed unused files from test harness
2e8a119 Merge pull request #186 from jakerella/feature-async-response
79eec03 Reorganized 'Documentation' section and renamed
...

Log Graphs


~$ git log --oneline --graph

*   714e0dd Merge pull request #220 from appendto/feature-two
|\
| * c8bcfc1 last update for feature two
| *   3e3a8fd Merge branch 'feature-two-tweak' into feature-two
| |\
| | * 46f4cf1 tweak for feature two
| * | 1471f2b one more thing on feature two
| |/
| * 5ce150b feature two initial work
|/
* 062b1f0 some previous work

Filtering the Log


~$ git log --no-merges

~$ git log --author="jakerella"

~$ git log --before="2014-07-01"

~$ git log -- src/js/

~$ git log -S foobar

Pointing Blame

(Many times at yourself...)

Blame Game


/* utility functions */

function sum(x, y) {
    return x * y;
}


~$ git blame src/js/utilities.js
d35241e6 (Ryan      2014-03-13   1) /* utility functions */
d35241e6 (Ryan      2014-03-13   2)
d35241e6 (Ryan      2014-03-13   3) function sum(x, y) {
27cc7225   (Jordan      2014-03-15     4)      return x * y;
d35241e6 (Ryan      2014-03-13   5) }

Blame Game


~$ git blame -L3,5 src/js/utilities.js
d35241e6 (Ryan      2014-03-13   3) function sum(x, y) {
27cc7225 (Jordan    2014-03-15   4)     return x * y;
d35241e6 (Ryan      2014-03-13   5) }

Dissecting the Log

Using `git bisect`

Using Bisect

First, switch to a broken branch...


~$ git bisect start


~$ git bisect bad


~$ git bisect good b9bdb02
Bisecting: 3 revisions left to test after this (roughly 2 steps)
[7e3f9393a716b1bf5c935031bae679249352726d] implemented some cool new thing


~$ git status
# Not currently on any branch.
nothing to commit (working directory clean)

Using Bisect

Test the current commit...


~$ git bisect good b9bdb02
Bisecting: 3 revisions left to test after this (roughly 2 steps)
[7e3f9393a716b1bf5c935031bae679249352726d] implemented some cool new thing


~$ grunt test


~$ git bisect [good|bad]
Bisecting: 1 revision left to test after this (roughly 1 step)
[b86e65d056ea750f1f882df7c10dc5e1bf2deeb2] risky change that may break things

Using Bisect


~$ git bisect start
~$ git bisect bad
~$ git bisect good b9bdb02
Bisecting: 3 revisions left to test after this (roughly 2 steps)
[7e3f9393a716b1bf5c935031bae679249352726d] implemented some cool new thing

...


~$ git bisect good
7e3f9393a716b1bf5c935031bae679249352726d is the first bad commit
commit 7e3f9393a716b1bf5c935031bae679249352726d
Author: jakerella

Now You Know...

Remember, we're no longer on a branch!


~$ git bisect reset
Previous HEAD position was b86e65d... Added some stuff
Switched to branch 'new-feature'

Playing Nice With Others

merge, rebase, and cherry-pick

Merging

With no divergent changes...

Fast Forward

With no divergent changes... we can "fast forward"


~$ git checkout master
~$ git merge feature


Updating b86e65d..d42c386
Fast forward
src/js/some-file.js |   13 ++++--+++
1 files changed, 7 insertions(+), 2 deletions(-)

No Fast Forward


~$ git checkout master
~$ git merge feature --no-ff

Why?

Because you lose branch/merge history with fast-forward!

Divergent Changes

When code in feature diverges from the current trunk...


~$ git checkout master
~$ git merge feature

Divergent Changes

When code in feature diverges from the current trunk...


~$ git checkout master
~$ git merge feature

Divergent Changes

When code in feature diverges from the current trunk...


~$ git checkout master
~$ git merge feature

Merge Conflicts

Conflicts

When git can't determine how to handle multiple changes...


~$ git checkout master
~$ git merge feature
Auto-merging README.md
CONFLICT (content): Merge conflict in README.md
Automatic merge failed; fix conflicts and then commit the result.

Conflicts

Inside the README.md file...


...some text common to both branches

<<<<<<< HEAD
text only in master
=======
same line, different text in branch
>>>>>>> feature

more common text...

Resolving the Conflict

Fix the conflict in the file!
Stage the fixed file
~$ git add README.md
Commit the files
(This is your merge commit, it may include other files!)
~$ git commit
Remove the "orig"inal file from the branch (if present)
~$ rm README.md.orig

Rebasing

BE CAREFUL rebasing if you have
already pushed to a shared branch!

Divergent Changes

Rewriting History

git rebase diagram with rewritten branch commits


~$ git checkout feature
~$ git rebase master

Rebasing on Master

git rebase diagram with rewritten commits on master


~$ git checkout feature
~$ git rebase master

You can still get conflicts with `rebase`!

Rebase Conflicts


~$ git rebase master

First, rewinding head to replay your work on top of it...
Applying: feature
error: patch failed: README.md:1
error: README.md: patch does not apply
Using index info to reconstruct a base tree...
Falling back to patching base and 3-way merge...
Auto-merging README.md
CONFLICT (content): Merge conflict in README.md
Failed to merge in the changes.

Resolving the Conflict

Fix the conflict in the file!
Stage the fixed file
~$ git add README.md
Commit the fix
~$ git commit
Continue the rebase
~$ git rebase --continue

Too Much Confliction?

You can abort the entire process...


~$ git rebase --abort

I don't always rebase, but when I do... I do it by default.


~$ git pull --rebase


~$ git config branch.master.rebase true
~$ git config branch.some-other-branch.rebase true
~$
~$ git config branch.autosetuprebase always

Cherry-picking

Multiple Branches


{{just spacing}}
{{just spacing}}

Cherry Pick


~$ git checkout new-feature
~$ git cherry-pick d42c386

Cherry Pick


~$ git branch -D old-feature

(Usually you don't want to cherry-pick
if you plan to use the source branch later!)

Thank You!