"Advanced" git

What: Advanced Git talk
Where: Philly *nix rwx Club
Who: John W. O'Brien
When: Mon, Apr 8, 2013

Outline

What makes up a repository
What makes up a commit
Analogies and conceptual models
Branching
Cherry-picking
Merging
Rebasing
Fast-forward merge
Bonus (time-permitting)
- Stashing
- Patching/Interactive adding

Level setting and caveats

Novice — Intermediate — Advanced

Everybody should get something out of this talk...
Required background

... provided you can find your way around a diff, know some basic data strutures, and can spell SCM or VCS.
Conceptual models vs. implementation details

Note well the difference.
Details omitted for clarity

Remotes, conflict resolution, tagging.

git's reputation

They say git gets easier once you get the basic idea that branches are homeomorphic endofunctors mapping submanifolds of a Hilbert space.
— Kornel (@pornelski) March 25, 2013

What makes up a repository

repo contents

Normal: Everything except the working tree is inside .git/.

Bare: .git/ is all there is.

What makes up a commit

commit contents

A commit's identity (it's SHA-1 digest) is intimately tied to its entire ancentry.

Analogies and conceptual models

"branch" is to "git" as...
1. "copy" is to "file"
2. "pointer" is to "C/C++"
3. "intersection" is to "road"
"checkout branch" is to "git" as...
1. "cd directory" is to "the file system"
2. "chmod g-rwx,o-rwx file" is to "access permissions"
3. "restore from last Friday" is to "data backups"

git builds the DAG

the DAG

Branching

Before

branch before commit

Branching

After

branch after commit

Cherry-picking

Before

before cherry-pick

Cherry-picking

After

after cherry-pick

Merging

Before

before merge

Merging

After

after merge

Rebasing

Before

before rebase

Rebasing

After

after rebase

Fast-forward merge

Before

before fast-forward merge

Fast-forward merge

After

after fast-forward merge

Stashing

Use stash instead of add and commit to defer commiting work-in-progress.
Think of stash as stack of local, disposable commits.
stash operates on tracked files only.

Patching/interactive adding

Like add but for control freaks.
Allows sub-file adding, patch splitting, and diff editing.