---

Gettin' Git

Fundamental Bits

The SHA

4b825dc642cb6eb9a060e54bf8d69288fbee4904

SHA-1

Takes some bunch of data, spits out the number.

Short SHA

5ab7499

(it's the beginning of the long SHA)

The Commit

% git log --pretty=raw

commit 24b00b520504c601eb2712949675a6be9660c939
tree 6d2b3d77b57c4abe9b90fb9649a155f39dcefda1
parent adca7904e00a2513c8eae9ba0fff9afb9732ed49
author Ed Chastain <echastain@blinkx.com> 1423527063 -0800
committer Ed Chastain <echastain@blinkx.com> 1423527063 -0800

A Big Tree of Changes

Refs

Remotes

Refers to whole repos
local "remote" is implicit

[remote "origin"]
        fetch = +refs/heads/*:refs/remotes/origin/*
        url = git@bitbucket.org:allenluce/ufe2.0.git
[remote "upstream"]
        fetch = +refs/heads/*:refs/remotes/upstream/*
        url = git@bitbucket.org:blinkxdev/ufe2.0.git
[branch "develop"]
        remote = origin
        merge = refs/heads/develop

Merge commit

Merging

Merge Hell

Rebasing

Rebasing basics

Merging lets you tie branches together.
Rebasing lets you cut them apart.
Rebasing rewrites history
Changes the SHAs of commits

The Rewriting Process

Pros/Cons

So there are some pretty great advantages to this. It'll let you keep an untangled and clean history. You can effectively merge in master whenever you want without worrying about making the branching graph worse.

One potential disadvantage that I've heard elsewhere is that when you rebase, you get the dates out of order. When git rebases, it keeps the same dates on the commits. So as you're shuffling things around, the dates get out of order. I've never had a huge problem with this in practice, as long as I keep in mind that things may have been rebased.

But the big downside is that you're rewriting history, which means you're rewriting the commit SHAs. When you do this, anything that might have those SHAs as parents will get discombobulated. That really means that whenever you rewrite history, you are throwing the past away entirely and creating a new reality.

The Good
- Lets you straighten things out
The Bad
- Rewrites history.

Rules of Thumb

Private? Yes.
Public? No.

Code Archeology

git blame 02fabc8~ SomeFile.php
git gui blame
blame parent

Blaming

-w to ignore whitespace changes -M to turn on the copy/paste detector -C to turn on the multifile copy-paste detector

Pickaxe

git log -p -S'ConversionKeys' phpfile.php

Bisection

Read the manual. Way useful.

Git Never Forgets (mostly)

reflog is your lifeline.
Where'd it go?

Reflog Knows

49dd9d8 HEAD@{2}: checkout: moving from 1eb5def41cfb1e1d81e6e884059e1878302e3a6a to 49dd9d8a65bc4
1eb5def HEAD@{3}: checkout: moving from develop to upstream/feature/UFE-2097
509d11f HEAD@{4}: merge refs/remotes/upstream/develop: Fast-forward
5e0d4db HEAD@{5}: checkout: moving from feature/UFE-2097 to develop

ReReRe

If you're doing a lot of the same merges, use it.