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

A "remote" is just a repo outside your local environment.

Cloning


~$ git clone git@github.com:jakerella/foo.git repo
        
~$ cd repo
        
~/repo$ git branch -a
* main
  remotes/origin/main

Cloning creates a remote called "origin",
which appears as a local branch.

Tracking

Any local branch can "track" a remote URL:


~/repo$ git branch -vv
* main               b956c45c [origin/main] Initial commit
  some-local-branch  a74b2950 Implemented that cool feature

Note the double "vv" here. A single "v" will not show you the remote branch being tracked.

Wherezitat?


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

Note we can have different URLs for fetching and pushing!

Going Upstream

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


~/repo$ git checkout -b new-feature
~/repo$ git branch --set-upstream-to=origin/new-feature
        
~/repo$ git push -u origin new-feature
        
~/repo$ git branch -vv
  main              b956c45c [origin/main] Initial commit
* new-feature       b956c45c [origin/new-feature] Initial commit
  some-local-branch a74b2950 Implemented that cool feature

Can there be other remotes?

Assume I've forked the Nodejs main repo...


~$ git clone git@github.com:jakerella/node.git
        
~/node$ git remote -v
origin  git@github.com:jakerella/node.git (fetch)
origin  git@github.com:jakerella/node.git (push)
        
~/node$ git remote add node-source git@github.com:nodejs/node.git
        
~/node$ git remote -v
origin         git@github.com:jakerella/node.git (fetch)
origin         git@github.com:jakerella/node.git (push)
node-source    git@github.com:nodejs/node.git (fetch)
node-source    git@github.com:nodejs/node.git (push)

Open Source Flow

This is the nature of open source development on Git.


~/node$ git fetch node-source
remote: Enumerating objects: 6018, done.
...
From github.com/nodejs/node
 * [new branch] ...
 ...
 * [new tag] ...
 ...
        
~/node$ git merge node-source/main
Updating 40f7a8ea..a479419b
...
        
~/node$ git checkout -b new-feature

Branch Differences

We commit some changes to our local feature branch.


~/node$ git diff main new-feature
        
diff --git a/README.md b/README.md
index a479419b..b5a9776f 100644
--- a/README.md
+++ b/README.md
@@ -1 +0,0 @@
-This is the readme
        
diff --git a/feature.js b/feature.js
new file mode 100644
index 0000000..b5a9776f
...

Branch Differences

What if that README change wasn't ours?


~$ git diff main new-feature

This is ALL changes between main and new-feature,
(regardless of what branch those came from).

Single-Branch Differences


~$ git diff main..new-feature
diff --git a/feature.js b/feature.js
new file mode 100644
index 00000000..b5a9776f
--- /dev/null
+++ b/feature.js
...

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


~/repo$ git commit -m "Added documentation"
[main (root-commit) b9bdb026] Added documentation
        
~/repo$ git log
commit b9bdb0261ee9bcaa31d7eb062c0bcafee3e530f0
Author: jdoe <john@doe.com>
Date:   Thu Jan 29 11:27:14 2026 -0400

Added documentation

Local Repos

Every local instance of a git repo has ALL of the data.

That means when GitHub goes down, you keep working...

...even with other people / machines.

A distributued VCS

https://docs.joomla.org/Dvcs

Fixing Changes Before Commit

Unstaged Changes


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

Unstaged Changes


~/repo$ git restore README.md
        
~/repo$ git status
On branch new-feature
nothing to commit, working tree clean

You can also restore entire directories:


~/repo$ git restore source/routes/

Unstaged Changes

Careful, NEW files will not be removed!


~/repo$ echo "testing" >> source/routes/test.js
~/repo$ git restore source/routes/
~/repo$ git status
On branch new-feature
Untracked files:
  (use "git add ..." to include in what will be committed)
       	sourc/routes/test.js

(You can just delete the file if not needed.)

Staged Changes


~/repo$ echo "foobar" >> README.md
~/repo$ git add README.md
        
~/repo$ git status
On branch new-feature
Changes to be committed:
  (use "git restore --staged <file>..." to unstage)
        modified:   README.md

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

Remember the Three States!

Fixing Things After Commit

Fixing commit messages


~/repo$ git commit -m "This is teh best"
[feature-branch 54af593b] This is teh best.
1 file changed, 1 insertion(+)


~/repo$ git commit --amend -m "This is the best"
[feature-branch 0486a7d6] This is the best.
1 file changed, 1 insertion(+)

Fixing commit messages


~/repo$ git commit -m "This is teh best"
[feature-branch 54af593b] This is teh best
1 file changed, 1 insertion(+)


~/repo$ git commit --amend -m "This is the best"
[feature-branch 0486a7d6] This is the best
1 file changed, 1 insertion(+)

What about the git log?


~/repo$ git log
commit 0486a7d61ee9bcaa31d7eb062c0bcafee3e530f0
Author: jdoe <john@doe.com>
Date:   Thu Jan 29 11:45:14 2026 -0400

This is the best

commit 72267fc26d88fa977d24760252da63b46ca3b81a
Author: fbar <foo@bar.com>
Date:   Wed Jan 28 09:45:10 2026 -0400

Bug fixes for older features

...

What if I forgot a file?

Stage it and amend it.


~/repo$ git add forgotten.js
        
~/repo$ git commit --amend
[new-feature 3e81873b] This is the best
 Date: Thu Jan 29 11:49:54 2026 -0400
 2 files changed, 1 insertion(+), 1 deletion(-)
 create mode 100644 forgotten.js

Caution When Amending!

If you push your bad change, then amend it, you might cause a nasty conflict for someone else.

Gone, but not forgotten


~/repo$ git log --oneline
3e81873b (HEAD -> new-feature) This is the best
72267fc2 (origin/main, origin/HEAD, main) Bug fixes for older features
        
~/repo$ git reflog
3e81873b HEAD@{0}: commit (amend): This is the best
0486a7d6 HEAD@{1}: commit (amend): This is the best
54af593b HEAD@{2}: commit: This is teh best.
72267fc2 HEAD@{3}: commit: Bug fixes for older features
...

What if I need to amend an older commit?

You'll need to use git rebase

Interactive Rebasing


~/repo$ git rebase --interactive HEAD^^^


pick 7e10e41c some old commit
pick 72267fc2 Bug fixes for older features
pick 3e81873b This is the best

# Rebase 5a39902..3e81873b onto 5a39902 (3 command(s))
#
# Commands:
# p, pick <commit> = use commit
# r, reword <commit> = use commit, but edit the commit message
# e, edit <commit> = use commit, but stop for amending
# s, squash <commit> = use commit, but meld into previous commit
...
# d, drop <commit> = remove commit
...

Interactive Rebasing


~/repo$ git rebase --interactive HEAD^^^


pick 7e10e41c some old commit
edit 72267fc2 Bug fixes for older features
pick 3e81873b This is the best

# Rebase 5a39902..3e81873b onto 5a39902 (3 command(s))
#
# Commands:
# p, pick <commit> = use commit
# r, reword <commit> = use commit, but edit the commit message
# e, edit <commit> = use commit, but stop for amending
# s, squash <commit> = use commit, but meld into previous commit
...
# d, drop <commit> = remove commit
...

Interactive Rebasing


~/repo$ git rebase --interactive HEAD^^^
Stopped at 72267fc2... Bug fixes for older features
You can amend the commit now, with
  git commit --amend
Once you are satisfied with your changes, run
  git rebase --continue

Now amend the commit just like before...


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

Interactive Rebasing

Careful! You changed all history from that amend forward.


~/repo$ git reflog

7650aafe HEAD@{0}: rebase -i (finish): returning to refs/heads/new-feature
7650aafe HEAD@{1}: rebase -i (pick): This is the best
bcb51f9a HEAD@{2}: commit (amend): Bug fixes for older features
72267fc2 HEAD@{3}: rebase -i: fast-forward
7e10e41c HEAD@{4}: rebase -i (start): checkout HEAD^^^
3e81873b HEAD@{5}: commit (amend): This is the best
0486a7d6 HEAD@{6}: commit (amend): This is the best
54af593b HEAD@{7}: commit This is teh best
72267fc2 HEAD@{8}: commit: Bug fixes for older features
7e10e41c HEAD@{9}: commit: some old commit

Understanding the Three Seashells States

Or... how to use reset for fun and profit.

Understanding the Three States

Understanding the Three States

git reset --soft HEAD^

`HEAD` is just a pointer

In fact, all branch names are just pointers!

And so are tags!

Soft Reset


~/repo$ git reset --soft HEAD^
~/repo$ git log
commit b86e65dab535623d487e063ef1337cfdecfaf99d
Author: jdoe <john@doe.com>
Date:   Wed Jan 28 09:45:10 2026 -0400

the immediately previous change (totally normal)
...
        
~/repo$ git status
On branch new-feature
Changes to be committed:
  (use "git restore --staged <file>..." to unstage)
        modified:   Readme.md

Understanding the Three States

git reset --mixed HEAD^

Mixed Reset


~/repo$ git reset --mixed HEAD^
~/repo$ git log
commit b86e65dab535623d487e063ef1337cfdecfaf99d
Author: jdoe <john@doe.com>
Date:   Wed Jan 28 09:45:10 2026 -0400

the immediately previous change (totally normal)
...
        
~/repo$ git status
On branch new-feature
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
        modified:   README.md

Understanding the Three States

git reset --hard HEAD^

Hard Reset


~/repo$ git reset --hard HEAD^
~/repo$ git log
commit b86e65dab535623d487e063ef1337cfdecfaf99d
Author: jdoe <john@doe.com>
Date:   Wed Jan 28 09:45:10 2026 -0400

the immediately previous change (totally normal)
...
        
~/repo$ git status
On branch new-feature
nothing to commit, working tree clean

Oh no!

I reset --hard and lost important work!

Git does not remove data easily.

Understanding the reflog


~/repo$ git reflog

b86e65da HEAD@{0}: reset: moving to HEAD^
d42c3864 HEAD@{1}: commit: this is not a good change
b86e65da HEAD@{2}: commit: the immediately previous change (totally normal)
b9bdb02f HEAD@{3}: checkout: moving from main to new-feature
b9bdb02f HEAD@{4}: commit: a really good change
        
~/repo$ git reset --hard HEAD@{1}
HEAD is now at d42c3864 this is not a good change

Understanding the reflog


~/repo$ git reflog

d42c3864 HEAD@{0}: reset: moving to HEAD@{1}
b86e65da HEAD@{1}: reset: moving to HEAD^
d42c3864 HEAD@{2}: commit: this is not a good change
b86e65da HEAD@{3}: commit: the immediately previous change (totally normal)
b9bdb02f HEAD@{4}: checkout: moving from main to new-feature
b9bdb02f HEAD@{5}: commit: a really good change
        
~$ 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')

Logs

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

The Basic Log


~/repo$ git log
commit d42c38691161f42fcc07d806f7df4579e8cd189e
Author: jakerella <me@example.com>
Date:   Fri Jan 30 13:57:36 2026 -0400

Added new API route to readme

commit b9bdb0261ee9bcaa31d7eb062c0bcafee3e530f0
Author: jakerella <me@example.com>
Date:   Thu Jan 29 09:14:16 2026 -0400

Various grammar edits to documentation
...

Log Options


~/repo$ git log --oneline

d42c3869 Added new API route to readme
b9bdb026 Various grammar edits to documentation
c2cb87e3 Remove unused files from test harness
2e8a119c Merge pull request #186 from jakerella/new-feature
79eec03a Reorganized documentation sections and renamed
...

Formatting and Graphing


~/repo$ git log --pretty="tformat:%h %as %an: %s" --graph

* 714e0dd9 2026-01-30 jakerella: Merge pull request #220 from foobar/feature-two
|\
| * c8bcfc14 2026-01-29 roro: last update for feature two
| * 3e3a8fdf 2026-01-28 jakerella: Merge branch 'feature-two-tweak' into feature-two
| |\
| | * 46f4cf12 2026-01-28 drnick: tweak for feature two
| * | 1471f2b8 2026-01-27 drnick: one more thing on feature two
| |/
| * 5ce150bc 2026-01-26 drnick: feature two initial work
|/
* 062b1f01 2026-01-25 roro: some previous work

Make it Easy

Add an alias to your bash or gitbash profile:


alias gl="git log --pretty='tformat:%h %as %an: %s' --graph"

Filtering the Log


~/repo$ git log --no-merges

~/repo$ git log --author="jakerella"

~/repo$ git log --before="2026-02-01"

~/repo$ git log -- source/routes

~/repo$ git log --grep=4\.31\.[0-9]+ -E

Pointing Blame

(Possibly at yourself...)

Blame Game


function divide(x, y) { ... }
function multiply(x, y) { ... }
function add(x, y) {
    return x + x;
}
function subtract(x, y) { ... }


~/repo$ git blame source/math.js
        
ca5dc559 (roro        2025-03-13   1) function divide(x, y) { ... }
ca5dc559 (roro        2025-03-13   2) function muiltiply(x, y) { ... }
d35241e6 (drnick      2026-01-22   3) function add(x, y) {
27cc7225 (jakerella   2026-01-29   4)     return x + x;
d35241e6 (drnick      2026-01-22   5) }
d35241e6 (drnick      2026-01-22   6) function subtract(x, y) { ... }

Blame Game

Know where to look?


~/repo$ git blame -L3,5 source/utilities.js

d35241e6 (drnick      2026-01-22   3) function add(x, y) {
27cc7225 (jakerella   2026-01-29   4)     return x + x;
d35241e6 (drnick      2026-01-22   5) }
        
~/repo$ git log --oneline source/utilities.js

27cc7225 Tweaked math add to double input
d35241e6 Expanded common math ops for new feature use
ca5dc559 Created helper file for common math ops

Playing Nice With Others

merge, rebase, and cherry-pick

Merging

With no divergent changes...

Fast Forward

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


~/repo$ git checkout main
~/repo$ git merge feature


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

No Fast Forward


~/repo$ git checkout main
~/repo$ git merge feature --no-ff

Why?

Because you lose merge history with fast-forward.

Divergent Changes

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


~/repo$ git checkout main
~/repo$ git merge feature

Divergent Changes

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


~/repo$ git checkout main
~/repo$ git merge feature

Divergent Changes

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


~/repo$ git checkout main
~/repo$ git merge feature

Divergent Changes

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


~/repo$ git log --oneline
c345d92 Merge pull request #123 from otheruser/new-feature
d42c386 Added new-feature to library
7a652d8 A piece of divergent work
b86e65d Some older work
...

Merge Conflicts

Conflicts

Git can't resolve multiple changes to the same lines.


~/repo$ git checkout main
~/repo$ git merge new-feature

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

Conflicts

Opening up the README.md file...


...some text common to both branches

<<<<<<< HEAD
text only in main
=======
same line, different text in branch
>>>>>>> new-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

Resolving the Conflict

Struggling to resolve the conflict?

Abort and ask for help!


~/repo$ git merge --abort

Rebasing

Rebasing rewrites commit history!

Divergent Changes

Rewriting History

git rebase diagram with rewritten branch commits


~/repo$ git checkout feature
~/repo$ git rebase main

Updating Main

We can update main with a fast-forward merge.

git rebase diagram with rewritten commits on main


~/repo$ git checkout main
~/repo$ git merge feature

You can still get conflicts with `rebase`!

Rebase Conflicts


~/repo$ git rebase main

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

Not going well?

You can abort the rebase just like a merge:


~/repo$ git rebase --abort

A recommendation...

If you plan to use rebase versus merge, always use rebase.


git pull  ===  git fetch && git merge


~/repo$ git pull --rebase


~$ git config branch.main.rebase true
~$ git config branch.another-branch.rebase true
        
~$ git config branch.autosetuprebase always

Cherry-picking

Multiple Branches


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

Cherry Pick


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

Cherry Pick

~$ git branch -D old-feature

Thank You!