Github - Git Training Slides: Foundations

Git FoundationsAn exploration of the Git toolbox
Ofﬁcialtrainingcurriculumv3.1.0©2012,GitHub,Inc.

Matthew McCullough
@matthewmccull

Ma hew who?
‣Open source contributor
‣Build tool book co-author
‣Continuous integration book co-author
‣5 year Git evangelist
‣VP of Training at GitHub

Welcome
‣Questions, Pacing
‣Ask questions at any time. Don't wait!
‣Suggest course pacing slowing/speeding up

Git
Where’s this coming from?

Git
-noun
British Slang. an unpleasant
or contemptible person
-Oxford English Dictionary
“
”

I'm an egotistical bastard, and I name
all my projects after myself.
First Linux, now git.
-Linus Torvalds
“
”

GIT - the stupid content tracker
"git" can mean anything, depending on your mood.
* random three-letter combination that is pronounceable, and not actually used by any
common UNIX command. The fact that it is a mispronunciation of "get" may or may not be
relevant.
* stupid. contemptible and despicable. simple. Take your pick from the dictionary of
slang.
* "global information tracker": you're in a good mood, and it actually works for you.
Angels sing, and a light suddenly fills the room.
* "goddamn idiotic truckload of sh*t": when it breaks
Git is a fast, scalable, distributed revision control system with an unusually rich
command set that provides both high-level operations and full access to internals.
Git is an Open Source project covered by the GNU General Public License. It was originally
written by Linus Torvalds with help of a group of hackers around the net. It is currently
maintained by Junio C Hamano.
“
”

Git?
centralized version control systems have matured

CVS
Subversion
PVCS
Perforce
Clear
CaseSource
Safe
RCS
Folders
Git?

small improvements, but no
radical innovation
Git?

I did end up using CVS for 7 years at a commercial
company and I hate it with a passion...
The slogan of Subversion for a while was
"CVS done right"... and if you start with that
kind of slogan, there's nowhere you can go.
There is no way to do CVS right.
-Linus Torvalds
“
”

50% Distributed Version Control
Git?
50% Git Concepts
with

Setting up Git
Check your Git version...
git --version

Setting up Git
binaries on your $PATH

Creating A Repository
# Green field project
$ git init newproject
$ cd newproject
# ...start coding

‣Create our ﬁrst repository

or if you already have source code

# Legacy project tree
$ cd existingproject
$ git init
# Add all the code
$ git add .
$ git commit -m”Initial import”

Contents of .git
.git
!"" COMMIT_EDITMSG
!"" HEAD
!"" MERGE_RR
!"" config
!"" description
!"" hooks
#   !"" pre-commit.sample
#   $"" update.sample
!"" index
!"" info
#   $"" exclude
!"" logs
#   !"" HEAD
#   $"" refs
#   $"" heads
#   $"" master
!"" objects
#   !"" 54
#   #   $"" 3b9bebdc6bd5c4b22136034a95dd097a57d3dd
#   !"" info
#   $"" pack
!"" refs
   !"" heads
   #   $"" master
   $"" tags

Three stage thinking
‣Explore the .git folder

Conﬁguring Git
Query existing conﬁguration

Conﬁguring Git
#List all config values
git config --list

Conﬁguring Git
#Query effective value of a single key
git config section.key
git config section.subsection.key

Conﬁguring Git
#Show a specific config value
git config user.name
git config user.email

Conﬁg Targets
git config --system
#Saves to /etc/gitconfig

Conﬁg Targets
git config --global
#Saves to ~/.gitconfig

Conﬁg Targets
git config --local
#Saves to .git/config

Conﬁguring Git
#Configure a setting in a .git repository
git config __________
git config --local __________
#Configure a setting in the user's home dir
git config --global __________
#Configure a setting in the Git install dir
# e.g. /usr/local/Cellar/git/1.7.x/etc/gitconfig
git config --system __________

Conﬁg Targets
Git conﬁguration reading & writing
targets local by default

Conﬁg Inheritance
Query existing conﬁguration by layer

Conﬁg Inheritance
#Query a single key in a single layer
git config --<WHERE> section.key
git config --<WHERE> section.subsection.key

Conﬁg Inheritance
#List all system config values
git config --system --list

Conﬁg Inheritance
#List all global config values
git config --global --list

Conﬁg Inheritance
#List all local config values
git config --local --list

Conﬁg Inheritance
#List effective config values
git config --list

Conﬁguration
Set user identity

Set User Identity
any conﬁg at any layer

Set User Identity
#List the current config
git config --global user.name "Fird Birfle"
git config --global user.email "fird@birfle.com"

Set User Identity
just a string

Set User Identity
user identity

Set User Identity
user identityauthenticationnot

Set User Identity
user identityauthenticationauthorizationnot

Set Console Color
console color

Set Console Color
git config --global color.ui always

Set Console Color
git log
--graph
--decorate
--simplify-by-decoration
--abbrev-commit
--date=relative
--pretty=oneline
--all

Conﬁguring Git
git log
--graph
--decorate
--abbrev-commit
--date=relative
--pretty=oneline
--all
| more

Set Console Color
output destination detection

Set Console Color
git config --global color.ui auto
# or the identical effect with...
git config --global color.ui true

Set Console Color
git log
--graph
--decorate
--abbrev-commit
--date=relative
--pretty=oneline
--all
| more

Set Console Color
when you need itColor

Set Console Color
only when you need itColor

Line Endings
default is to do nothing

Line Endings
http://help.github.com/dealing-with-lineendings/

Line Endings
#Force files to be LF in the repo,
# even on Mac/Linux
git config --global core.autocrlf input
#Force Windows to convert to platform
# on checkout and to LF on commit
git config --global core.autocrlf true

Line Endings
#Force files to be LF during `add`
git config --global core.autocrlf input
#Force Windows to convert to CRLF
# on checkout and to LF on `add`
git config --global core.autocrlf true

Line Endings
#Never complain about line ending conversion
git config --global core.safecrlf false
#Warn, but allow line ending conversion to proceed
#(the default)
git config --global core.safecrlf warn
#Do not allow line ending conversion to proceed
git config --global core.safecrlf true

Conﬁguration
Secure Sockets Host (SSH)

Conﬁguring SSH
‣Generate an ssh key pair

Conﬁguring SSH
$ ssh-keygen -t rsa -C”For GitHub”

Conﬁguring SSH
# Verify the files were created
$ cd ~/.ssh
$ ls

Conﬁguring SSH
‣id_rsa is the private half of the key
‣Keep this uncompromisingly secret
‣id_rsa.pub is the public half of the key
‣Give this away freely

Conﬁguring SSH
#GitHub sanity test
ssh -T git@github.com
> Hi matthewmccullough! You've successfully
authenticated, but GitHub does not provide
shell access.

Conﬁguring SSH
#GitHub sanity test with verbose SSH
ssh -v git@github.com
>OpenSSH_5.2p1, OpenSSL 0.9.8l 5 Nov 2009
debug1: Reading configuration data /Users/mccm06/.ssh/config
debug1: Reading configuration data /etc/ssh_config
debug1: Connecting to github.com [207.97.227.239] port 22.
debug1: Connection established.
debug1: identity file /Users/mccm06/.ssh/identity type -1
debug1: identity file /Users/mccm06/.ssh/id_rsa type 1
debug1: identity file /Users/mccm06/.ssh/id_dsa type 2
...
debug1: Host 'github.com' is known and matches the RSA host key.
debug1: Found key in /Users/mccm06/.ssh/known_hosts:3
debug1: ssh_rsa_verify: signature correct
...
debug1: Trying private key: /Users/mccm06/.ssh/identity
debug1: Offering public key: /Users/mccm06/.ssh/id_rsa
debug1: Remote: Forced command: gerve matthewmccullough

Using Git
Three Stage Thinking

‣Edit
‣Add
‣Commit

Working Staging Repo
add
commit
edit

‣shopping cart
‣put things in
‣take things out
‣purchase at register

‣database transaction
‣update values
‣insert rows
‣delete rows
‣commit transaction

only onestaging area

Commit Message Editor
an alternate editor?

$EDITOR environment variable
O
ption
1

$ export EDITOR=<AnEditorOnYourPath>
O
ption
1

GitPad wraps Notepad (or $EDITOR)
O
ption
2

http://github.com/github/GitPad
O
ption
2

Run GitPad
...registers & wraps Notepad as the editor
O
ption
2

Git-speciﬁc conﬁguration option
O
ption
3

#for TextMate on Mac
git config --global core.editor "mate -w"
#for Notepad2 on Windows
git config --global core.editor "notepad2.exe"
#for emacs on Linux
git config --global core.editor "emacs"
O
ption
3

O
ption
3

‣Toggle to alternate editor
‣Make a commit
‣Test that the new editor pops up

Usage Basics
Adding & committing code

$ vi first.html
$ git status
$ git add first.html
$ git commit -m”First commit”

‣Write a sample HTML or TXT ﬁle
‣Inspect Git’s status
‣Add code (stage it)
‣Commit code

What has changed that we
haven’t committed?

# Show the unstaged changes
$ git diff

$ git diff

# Show the staged changes
$ git diff --staged

$ git diff --staged

# Show uncommitted changes
$ git diff HEAD

$ git diff HEAD

Usage Basics
Limiting diff output

Limiting Diff Output
Word changes instead of entire lines?

git diff --color-words

$ git diff
diff --git a/first.txt b/first.txt
index cbb1543..e99dea9 100644
--- a/first.txt
+++ b/first.txt
@@ -1,4 +1,4 @@
-//Round the rugged rock
+//Round the ragged rock
$ git diff --color-words
--- a/first.txt
+++ b/first.txt
@@ -1,4 +1,4 @@
//Round the ruggedragged rock

git diff --word-diff

$ git diff
--- a/first.txt
+++ b/first.txt
@@ -1,4 +1,4 @@
-//Round the rugged rock
+//Round the ragged rock
$ git diff --word-diff
--- a/first.txt
+++ b/first.txt
@@ -1,4 +1,4 @@
//Round the [-rugged-]{+ragged+} rock

whitespace suppressed?

refactoring review

git diff -w

$ git diff
index 09195c0..f2c3243 100644
--- a/first.txt
+++ b/first.txt
@@ -1,4 +1,4 @@
-//Foo
-//Bar
-//Baz
+ //Foo
+// Bar
+//Baz▊
$ git diff -w
$

Usage Basics
Limiting diff by type

# Added (A)
# Copied (C)
# Deleted (D)
# Modified (M)
# Renamed (R)
# Type changed (T)
# Unmerged (U)
# Unknown (X)
# Pairing Broken (B)
# Only show changes in added files
git diff --diff-filter=A

# Added (A)
# Copied (C)
# Deleted (D)
# Modified (M)
# Renamed (R)
# Type changed (T)
# Unmerged (U)
# Unknown (X)
# Only show changes in modified files
git diff --diff-filter=M

# Added (A)
# Copied (C)
# Deleted (D)
# Modified (M)
# Renamed (R)
# Type changed (T)
# Unmerged (U)
# Unknown (X)
# Only show changes in added or modified files
git diff --diff-filter=AM

$ git status -s -u
D README
MM first.txt
$ git diff --diff-filter=M
index 71b55ef..14e4853 100644
--- a/first.txt
+++ b/first.txt
@@ -1,3 +1,3 @@
-//Foo
//Bar
+//Baz
Only ﬁrst.txt is
reported

Usage Basics
Reviewing history

view history of commits

# Show all history
git log

# Show all history with filenames
git log --stat

# Show all history with patches
git log --patch
git log -p

# Limit the output entries
git log -1
git log -3
git log -5

# Control the output format
git log --pretty=full

git log --pretty=fuller

git log --pretty=email

git log --pretty=raw

git log --pretty=format:<pattern>

# Limit the output to added files
git log --diff-filter=A

Ignoring Files
Untracked Tracked
Unmodiﬁed
Tracked
Modiﬁed
Tracked
Staged
Ignored
commit
add
edit
add
rm
ignore

Ignoring Files
suppressing ﬁles from being
reported as untracked

Ignoring Files
$ vim .gitignore
#Add glob patterns, one per line
*.log
*.tmp

Ignoring Files
in-memory recursive evaluation

Ignoring Files
$ vim .gitignore
#Add glob patterns, one per line
*.log
*.tmp
target
output/
!special.log

Ignoring Files
‣Ignore ﬁles via local .gitignore

Usage Basics+
Open source .gitignores

Open Source Ignores
Preconﬁgured .gitignore ﬁles

Open Source Ignores
http://github.com/github/gitignore

copy and paste(the one time it’s OK to do it)

Global Ignore
Global .gitignore ?

Global Ignore
$ git config --global
core.excludesfile "~/.gitignore"

Global Ignore
$ vim ~/.gitignore
# Operating system and editor temp files
# Generally redundant over project .gitignores
thumbs.db
.DS_Store

Global Ignore
‣Ignore ﬁles via global ~/.gitignore

The Git File Workflow
Untracked Tracked
Unmodified
Tracked
Modified
Tracked
Staged
Ignored
commit
add
edit
add
rm
ignore

Removing Files

# Directly remove & stage
$ git rm <FILENAME>

# Remove with OS or tool,
# not integrated with Git
$ rm <FILENAME>
# Staging area says it is
# deleted but not staged
$ git status
# Put deletion into staging
$ git rm <FILENAME>

# Remove with OS or tool
# then follow up with git add
$ rm <FILENAMES>
$ git add -u .

‣ Remove ﬁles

Moving Files

# Directly move & stage
$ git mv <FILENAME> <NEWFILENAME>

# Move with OS or tool,
mv <FILENAME> <NEWFILENAME>
# Then follow up with git add
git add -A .

‣ Rename (move) ﬁles
‣ View history of the move

Usage Basics+
Similarity index

Similarity Index
no "move" primitive

Similarity Index
“similarity index”

Similarity Index
score of sameness

Usage Basics+
Similarity index for moves

Similarity Index
# Move with OS or tool,
$ mv <FILENAME> <NEWFILENAME>
# Follow up by staging everything
$ git add -A .
# Renames showing
git status
# No renames showing?
git log --stat

Similarity Index
# Renames shown
git log --stat -M

Similarity Index
‣ Rename (move) ﬁles with changes
‣ Essentially, a refactoring workﬂow

Usage Basics+
Similarity index for copies

Similarity Index
# Copies & renames shown
# (superset of -M)
git log --stat -C

Similarity Index
‣Copy a ﬁle to a new ﬁlename
‣Add and commit it
‣Log it using our -C option

“For performance reasons, by
default, -C option finds
copies only if the original file
of the copy was modified in
the same changeset.
”

Similarity Index
‣Modify a ﬁle and copy it (in the same commit)
‣Log using the -C option

“The --find-copies-harder flag makes the
command inspect unmodified files as
candidates for the source of copy. This
is a very expensive operation for large
projects, so use it with caution. Giving
more than one -C option has the same
effect.
”

Similarity Index
# Copies & renames shown
# (superset of -M)
git log --stat -C -C
git log --stat --find-copies-harder

Similarity Index
‣Log the same ﬁle using our -C -C option

Usage Basics+
Similarity index for blame

Similarity Index
# File authoring shown
git blame rerere.c

Similarity Index
# True source of code shown
git blame rerere.c -C

Similarity Index
5b2fd956 (Stephan Beyer 2008-07-09 14:58:57 +0200 1) #include "cache.h"
c455c87c (Johannes Schindelin 2008-07-21 19:03:49 +0100 2) #include "string-list.h"
5b2fd956 (Stephan Beyer 2008-07-09 14:58:57 +0200 3) #include "rerere.h"
5b2fd956 (Stephan Beyer 2008-07-09 14:58:57 +0200 4) #include "xdiff-interface.h"
dea4562b (Junio C Hamano 2009-12-25 15:51:32 -0800 5) #include "dir.h"
dea4562b (Junio C Hamano 2009-12-25 15:51:32 -0800 6) #include "resolve-undo.h"
dea4562b (Junio C Hamano 2009-12-25 15:51:32 -0800 7) #include "ll-merge.h"
8588567c (Junio C Hamano 2010-01-16 23:28:46 -0800 8) #include "attr.h"
5b2fd956 (Stephan Beyer 2008-07-09 14:58:57 +0200 9)
ac49f5ca (Martin von Zweigbergk 2011-02-16 05:47:44 -0500 10) #define RESOLVED 0
ac49f5ca (Martin von Zweigbergk 2011-02-16 05:47:44 -0500 11) #define PUNTED 1
ac49f5ca (Martin von Zweigbergk 2011-02-16 05:47:44 -0500 12) #define THREE_STAGED 2
ac49f5ca (Martin von Zweigbergk 2011-02-16 05:47:44 -0500 13) void *RERERE_RESOLVED = &RERERE_RESOLVED;
ac49f5ca (Martin von Zweigbergk 2011-02-16 05:47:44 -0500 14)
5b2fd956 (Stephan Beyer 2008-07-09 14:58:57 +0200 15) /* if rerere_enabled == -1, fall back to detection of .git
5b2fd956 (Stephan Beyer 2008-07-09 14:58:57 +0200 16) static int rerere_enabled = -1;
5b2fd956 (Stephan Beyer 2008-07-09 14:58:57 +0200 18) /* automatically update cleanly resolved paths to the inde
5b2fd956 (Stephan Beyer 2008-07-09 14:58:57 +0200 19) static int rerere_autoupdate;
5b2fd956 (Stephan Beyer 2008-07-09 14:58:57 +0200 21) static char *merge_rr_path;
90056966 (SZEDER Gábor 2009-02-14 23:21:04 +0100 23) const char *rerere_path(const char *hex, const char *file)
5b2fd956 (Stephan Beyer 2008-07-09 14:58:57 +0200 24) {
90056966 (SZEDER Gábor 2009-02-14 23:21:04 +0100 25) return git_path("rr-cache/%s/%s", hex, file);
5b2fd956 (Stephan Beyer 2008-07-09 14:58:57 +0200 26) }

Similarity Index
5b2fd956 rerere.c (Stephan Beyer 2008-07-09 14:58:57 +0200 1) #include "cache.h"
c455c87c rerere.c (Johannes Schindelin 2008-07-21 19:03:49 +0100 2) #include "string-list.h"
5b2fd956 rerere.c (Stephan Beyer 2008-07-09 14:58:57 +0200 3) #include "rerere.h"
5b2fd956 rerere.c (Stephan Beyer 2008-07-09 14:58:57 +0200 4) #include "xdiff-interface.h"
dea4562b rerere.c (Junio C Hamano 2009-12-25 15:51:32 -0800 5) #include "dir.h"
dea4562b rerere.c (Junio C Hamano 2009-12-25 15:51:32 -0800 6) #include "resolve-undo.h"
dea4562b rerere.c (Junio C Hamano 2009-12-25 15:51:32 -0800 7) #include "ll-merge.h"
8588567c rerere.c (Junio C Hamano 2010-01-16 23:28:46 -0800 8) #include "attr.h"
5b2fd956 rerere.c (Stephan Beyer 2008-07-09 14:58:57 +0200 9)
ac49f5ca rerere.c (Martin von Zweigbergk 2011-02-16 05:47:44 -0500 10) #define RESOLVED 0
ac49f5ca rerere.c (Martin von Zweigbergk 2011-02-16 05:47:44 -0500 11) #define PUNTED 1
ac49f5ca rerere.c (Martin von Zweigbergk 2011-02-16 05:47:44 -0500 12) #define THREE_STAGED 2
ac49f5ca rerere.c (Martin von Zweigbergk 2011-02-16 05:47:44 -0500 13) void *RERERE_RESOLVED = &RERERE_RESOLVED;
ac49f5ca rerere.c (Martin von Zweigbergk 2011-02-16 05:47:44 -0500 14)
b4372ef1 builtin-rerere.c (Johannes Schindelin 2007-07-06 13:05:59 +0100 15) /* if rerere_enabled == -1, fall back to detection of .git
b4372ef1 builtin-rerere.c (Johannes Schindelin 2007-07-06 13:05:59 +0100 16) static int rerere_enabled = -1;
b4372ef1 builtin-rerere.c (Johannes Schindelin 2007-07-06 13:05:59 +0100 17)
121c813f builtin-rerere.c (Junio C Hamano 2008-06-22 02:04:31 -0700 18) /* automatically update cleanly resolved paths to the inde
121c813f builtin-rerere.c (Junio C Hamano 2008-06-22 02:04:31 -0700 19) static int rerere_autoupdate;
121c813f builtin-rerere.c (Junio C Hamano 2008-06-22 02:04:31 -0700 20)
658f3650 builtin-rerere.c (Johannes Schindelin 2006-12-20 17:39:41 +0100 21) static char *merge_rr_path;
658f3650 builtin-rerere.c (Johannes Schindelin 2006-12-20 17:39:41 +0100 22)
90056966 rerere.c (SZEDER Gábor 2009-02-14 23:21:04 +0100 23) const char *rerere_path(const char *hex, const char *file)
5b2fd956 rerere.c (Stephan Beyer 2008-07-09 14:58:57 +0200 24) {
90056966 rerere.c (SZEDER Gábor 2009-02-14 23:21:04 +0100 25) return git_path("rr-cache/%s/%s", hex, file);
5b2fd956 rerere.c (Stephan Beyer 2008-07-09 14:58:57 +0200 26) }
5b2fd956 rerere.c (Stephan Beyer 2008-07-09 14:58:57 +0200 27)

Offline
‣Local repository is a full copy of the remote
‣Clone fetches all branches and tags
‣Almost all activities happen offline (local disk)
‣Offline activities are push-ed to remotes

More demand to work without
connectivity?

Ofﬂine
nice beneﬁt,
but wrong reason

Ofﬂine
batched network access

Ofﬂine
Checkout a branch
Add changes
Commit changes
Branch changes
Log history
Grep history
Stash pending changes
Tag a commit
Remove a ﬁle
Merge a branch
Rewrite history

Ofﬂine
give up incremental revision numbers

Ofﬂine
‣ Using every command ofﬂine

Cloning Repositories
‣Git supports many cloning protocols
‣ﬁle
‣git
‣ssh
‣http

‣ﬁle
‣git clone file://myrepos/project
‣git clone /myrepos/project

‣git
‣git clone git://server/project.git

‣ssh
‣ git clone git+ssh://user@server:project.git
‣ git clone user@server:project.git

‣http (dumb)
‣git clone http://server/project.git
‣git clone https://server/project.git

‣http (smart)
‣git clone http://server/project.git
‣git clone https://server/project.git

‣ Clone hellogitworld
‣ git clone

‣Git Conﬁguration
‣git config --global http.proxy “<URL>”

‣git: git
‣hg: mercurial
‣bzr: bazaar

data from http://whygitisbetterthanx.com/#git-is-fast
git svn
Init
git svn
Status
git svn
Diff
git svn
Tag
git svn
Log
git svn
Commit (Lg)
git svn
Commit (Sm)
git c svn c
Branch
Speed

Speed
‣ Add, commit and push 1000 ﬁles

Namespaces
Local Remote Upstream

Namespaces
#List local branches
git branch

Namespaces
#List remote branches
git branch -r

Namespaces
#List all branches
git branch -a

Namespaces
#List upstream branches
git ls-remote origin

Namespaces
commit
fetch
push
clone clone clone
push
pull pull pull

Namespaces
‣git commit
‣Transactionally save code snapshot
‣Commit to local branch
‣Operate on local disk

Namespaces
‣git push <remote>
‣Send code to an upstream server
‣Update remote branches

Namespaces
‣git pull <remote>
‣Retrieve upstream objects
‣Update remote branch
‣Merge changes into local branch
‣Commit the merge to the local branch

Remotes
Remotes are just symbolic names

Remotes
You can have as many as you like

Remotes
The default name is origin if you’ve cloned

Remotes
Remote-tracking branches are locally immutable
(conceptually)

Remotes
‣ Adding remotes
‣ Fetching from remotes (upstream)

‣ Purge remote branches that have been removed from an
upstream repository
‣git remote prune <REMOTENAME>

Remotes
‣Deleting upstream branches
‣Pruning locally

Architecture
Plumbing and Porcelain

Plumbing and Porcelain
Command Composition

Plumbing is the set of low level utilities
Command Composition

Porcelain is the set of end user commands
Command Composition

Porcelain is comprised of plumbing
Command Composition

git-add git-am git-archive git-bisect git-branch git-bundle git-
checkout git-cherry-pick git-citool git-clean git-clone git-commit
git-describe git-diff git-fetch git-format-patch git-gc git-grep git-
gui git-init git-log git-merge git-mv git-notes git-pull git-push git-
rebase git-reset git-revert git-rm git-shortlog git-show git-stash
git-status git-submodule git-tag gitk git-config git-fast-export git-
fast-import git-filter-branch git-lost-found git-mergetool git-pack-
refs git-prune git-reflog git-relink git-remote git-repack git-replace
git-repo-config git-annotate git-blame git-cherry git-count-objects
git-difftool git-fsck git-get-tar-commit-id git-help git-instaweb git-
merge-tree git-rerere git-rev-parse git-show-branch git-verify-tag
git-whatchanged git-archimport git-cvsexportcommit git-cvsimport git-
cvsserver git-imap-send git-quiltimport git-request-pull git-send-
email git-svn
Porcelain
git-apply git-checkout-index git-commit-tree git-hash-object git-index-pack git-merge-file
git-merge-index git-mktag git-mktree git-pack-objects git-prune-packed git-read-tree git-
symbolic-ref git-unpack-objects git-update-index git-update-ref git-write-tree git-cat-file
git-diff-files git-diff-index git-diff-tree git-for-each-ref git-ls-files git-ls-remote git-
ls-tree git-merge-base git-name-rev git-pack-redundant git-rev-list git-show-index git-show-
ref git-tar-tree git-unpack-file git-var git-verify-pack git-daemon git-fetch-pack git-http-
backend git-send-pack git-update-server-info git-http-fetch git-http-push git-parse-remote
git-receive-pack git-shell git-upload-archive git-upload-pack git-check-attr git-check-ref-
format git-fmt-merge-msg git-mailinfo git-mailsplit git-merge-one-file git-patch-id git-peek-
remote git-sh-setup git-stripspace
Plumbing

pull is comprised of fetch + merge
Command Composition

checkout -b is comprised of branch + checkout
Command Composition

log HEAD is comprised of rev-parse + log
Command Composition

Aliases
‣Shortcuts for common commands
‣Create your own recipe
‣Largely the same as shell aliases

Aliases
# Alias for status as 's'
git config --global alias.s "status -u -s"

Aliases
# Alias for log with file name as 'l'
git config --global alias.l "log --stat -C"

Aliases
# Alias showing all branches to 'br'
git config --global alias.br "branch -a"

Aliases
# Alias for commit-no-staging to 'cns'
git config --global alias.cns "commit -a"

Aliases
# Alias for shell pull then push to 'sync'
$ git config --global alias.sync
"!git pull && git push"

Aliases
# Alias for crummy-commit-file-quick
$ git config --global alias.ccfq
"!sh -c 'git add $1 && git commit -m"Placeholder"' -"

Aliases
‣ Matthew's Aliases
‣ https://github.com/matthewmccullough/git-workshop/blob/master/
workbook/examples/conﬁg/.gitconﬁg

Typical SCMs use delta storage
Storage

CVS / Subversion / darcs / Mercurial
Storage

Storage
v1 v2 v3 v4
File A
File B
File C
File A
File B File B
File C
v5
File A
File BFile B
Δ Δ
Δ
Δ ΔΔΔ

Checkin
Checkin Checkin
Checkin
Checkin
Checkin
Checkin
Checkin
Checkin
Checkin
Checkin
Delta storage gets slower as the history of a ﬁle gets
longer
Storage

Directed Acyclic Graph
Storage

Copy of the entire tree per checkin
Storage

cp -r srcfolder srcfolder.prev
Storage

Storage
v1 v2 v3 v4
File A
File B
File C
File A
File B File B
File C
v5
File A
File BFile B
File A File A
File C File C File C

hard link to existing identical blobs
Storage

Storage
v1 v2 v3 v4
File A
File B
File C
File A
File B File B
File C
v5
File A
File BFile B
File A File A
File C File C File Cß

zlib deﬂates each blob at commit
Storage

zlib deﬂates the entire repo
Storage

Storage
2100 MBbecame
205 MB
Act I

Hashes
centralized VCSs use sequential revision numbers

40 hex characters
(20 bytes)
Hashes

9AB223D28B1AA46EF1780B22F304982E39872C34
Hashes

Hashes
9AB223D28B1AA46EF1780B22F304982E39872C34
<html>
<body>
<p>This is a test</p>
<img src="http://ai.com/icon.gif">
</body>
</html>
9AB223D28B1AA46EF1780B22F304982E39872C34

use as little of it as is unique
Hashes

commitish
Hashes
= shorthand for commit hashes

treeish
Hashes
= shorthand for tree hashes

9AB22F
a certain commit
Hashes

9AB22F^
one commit before a certain commit
Hashes

9AB22F^^
two commits before a certain commit
Hashes

9AB22F~5
ﬁve commits before a certain commit
Hashes

9AB223..56CD77
between these two commits
Hashes

HEAD
the most recent commit on this branch
Hashes

HEAD^
one commit before the most recent commit
Hashes

HEAD~2
two commits before the most recent commit
Hashes

HEAD..HEAD^^^
between the given recent commits
Hashes

master
the most recent commit on this branch
Hashes

master^^
two commits before the most recent commit on this branch
Hashes

master~5
ﬁve commits before the most recent commit on this branch
Hashes

remotes/origin/master
the most recent commit on this remote tracking branch
Hashes

origin/master
the most recent commit on this remote tracking branch
Hashes

Hashes
Navigate with commitish on
commit, status, & log

Architecture
Hash relationships

Hashes
‣Blob
‣Tree
‣Commit
‣Tag

Hashes
tree
tree: 7e8b1 web
blob: 9ab16 index.html
a10b3
tree
blob: 8d162 logo.jpg
blob: 51d22 draw.js
7e8b1commit
tree: a10b3
parent: nil
author: Fird
committer: Matthew
message:
Major refactoring
of the web content.
c67db
blob<html>
<body></body>
</html>
9ab16
blob
//Some more javascript
var renderSize
51d22
blob
7D 8D B3 7F BD 12 9F E9
7B 78 9D 3F 5C A6 72 CB
8d162

Hashes
v1 v2 v3
commit
tree: 9a87b
parent: nil
author: Fird
committer: Matthew
message:
Major refactoring
of the Javascript rendering
engine.
c67db
commit
tree: b22c1
parent: c67db
author: Tim
committer: Fird
message:
Minor update to HTML
9bd21
commit
tree: b22c1
parent: 9bd21
author: Johnny
committer: Joe
message:
New language transations
1c2d7

Hashes
RELEASE_1.0 HEAD
bug979branch
commit
c67db
commit
9bd21
commit
1c2d7
commit
8c2d1
commit
1bdcd
commit
2daa1

Branches
default branch name is master

Branches
master doesn’t have any special privileges

Branches

Branches
# Creating a branch
git branch <BRANCHNAME>

RELEASE_1.0 HEAD
bug979branch
commit
c67db
commit
9bd21
commit
1c2d7
commit
8c2d1
commit
1bdcd
commit
2daa1

Hashes
‣Create a new local branch from HEAD

Branches
# Creating a branch
git branch <BRANCHNAME> HEAD

Branches
# Creating a branch
git branch <BRANCHNAME> <REF>

Hashes
‣Create a new local branch from a branch

Branching
Branch as experiments

Branches
What do cheap branches enable?

Branches
‣Experimentation
‣

Branches
‣Experimentation
‣Safe experimentation

Branches
Better reuse of units of work

Hashes
‣Create a branch for an experiment
‣Delete the failed experiment

Branches
When should you branch?

Branches
Branches isolate volatile work

Branches
Branches cost a mere 20 bytes

Branches
We’ve always wanted to branch often
It’s just been too expensive, polluting, or ceremonious

Hashes
‣Show branches on the Git project

Branches
‣Branched by lifetime
‣ Product
‣ Integration
‣ Feature
‣ Story
‣ Idea

Branches
product
integration
feature
story
idea

product
v1.0 integration
story1 story2
v1.5 integration
story3
Branches

Branches
Integ
Product
Integ
Product
Integ
Product

Branches
Idea
Story
Feature FeatureFeature
Integ
Product
Integ
Product
Integ
Product

Branches
‣Branch from the master branch
‣Merge from the topic branch
‣Destroy the topic branch

Stash
‣Numbered branch
‣Stack based implementation
‣Push, Peek, and Pop operations
(But has direct entry access too)

Stash
# Stash your pending changes
git stash

Stash
# List your stashes
git stash list

Stash
# Stash your pending changes
git stash save “<Message>”

Stash
# Merge & delete the latest stash
git stash pop

Stash
# Merge & delete a stash
git stash pop stash@{0}

Stash
# Merge & keep the latest stash
git stash apply

Branches
‣Stash modiﬁed changes
‣Stash staged changes
‣Apply stashed changes

Stash
# Convert a stash to a branch
git stash branch <newbr>

Stash
# Convert a stash to a branch
git stash branch <newbr> stash@{3}

Branches
‣Convert a stash to a branch

tags as a ﬁrst class data type

Tagging
‣Tagging at each level of approval
‣Dev
‣CM
‣QA
‣Production

Tagging
reference,
annotated and
signed tag types

Tagging
# Tag HEAD
git tag <TAGNAME>

Tagging
# Tag an existing ref
git tag <TAGNAME> <REF>

Tagging
# List known tags
git tag

Tagging
# Show a tag’s contents
git show tag

Tagging
‣Tag a revision
‣Start a branch from a tag

Tagging
‣Tag a revision with an annotated tag

Tagging
‣Tag a revision with a signed tag

Tagging
Tags don't push by default

Tagging
# Push all tags
git push <remote> <tag>

Tagging
# Push all tags
git push --tags

‣Push a speciﬁc tag
‣Push all tags

Tagging
Tags do fetch by default

Tagging
but the refspec doesn’t say to

‣Inspect .git/conﬁg refspec

Merging
very traditional merge of a branch

Merging
git checkout master
git merge <featurebranch>

a32
2e2
e69
d19
8b3
Branch
Master/Trunk/MainLatest
Merging
Recursive
Merge
9f1 Mergee698b3

strategy: recursive
result: no conﬂicts

a32
e69
d19
Branch
Merging
Fast Forward
Merge
Merge

a32
e69
d19
Merging
FF
Merge

strategy: recursive
result: fast forward

a32
2e2
e69
d19
8b3
Branch
Merging
Conflicting
Merge
Merge
9f1
e698b3
Fix Conﬂict

strategy: recursive
result: conﬂicting

Merging
git checkout master
git merge <fb1> <fb2> <fb3>

Merging
git checkout master
git merge -s subtree <fb1>

Merging
git checkout master
git merge --squash -s subtree <fb1>

Tagging
‣Merge a local branch
‣Merge a remote branch

rebasing is not a merge
Rebasing

rebasing is a preparation for a merge
Rebasing

Merges weave multiple old changes into
a new unifying commit
Rebasing

Rebase reorders the chosen commits
before your branch work
Rebasing

simulates team members taking turns working
(one person at a time)
Rebasing

Retrieve upstream changes and
relocate your local changes to the end
Rebasing

Rebasing
git pull --rebase
# is the same as
git checkout master
git rebase origin/master

Rebasing
git checkout <featurebranch>
git rebase master

a32
2e2
8b3
Rebasing
e69
d19
Branch

a32
2e2
8b3
e69
d19
Branch
Rebase
Rebasing

a32
2e2
e69'
d19'
8b3 Branch
Rebasing
Rebase

a32
2e2
e69'
d19'
8b3 Branch
Merge
Rebasing

Rebasing
‣Rebase topic branch on master

Rework your work so it

makes sense to the team
Rebasing

Rebasing
git checkout myfeaturebranch
# Replay the last 5 commits
git rebase -i HEAD~5

a32
2e2
8b3
Rebasing
e69
d19

a32
2e2
Rebasing
e69
d19

a32
Rebasing
e69
d19
2e2

Rebasing
‣Interactively rebase a single branch

Usage Models
Central
Repo
Centralized

Usage Models
Blessed
Repo
Dictatorship

Usage Models
Certiﬁed
Repo
Development Repo
ntegrationManaged
Continuous
Integration
Server

Usage Models
Custom+PublicContrib
Customized
PrivatePublic
GitHub

Usage Models
Mirror
Development Repo
Mirrored
Mirror
Certiﬁed
Repo

Clean
clean purges untracked ﬁles
respects ignored and tracked

Clean
# Dry-run remove files
git clean -n

Clean
# Dry-run remove files, dirs
git clean -nd

Clean
# Remove files
git clean -f

Clean
# Remove files, dirs
git clean -fd

Undo
‣Clean untracked ﬁles

Clean
# Also remove ignored files
git clean -xf

Clean
# Also remove ignored files, dirs
git clean -xdf

Clean
# Only list ignored files
git clean -Xn

Clean
# Only remove ignored files
git clean -Xf

Revert
revert negates one or more commits

Revert
new commit at the end of HEAD

Revert
no pointer to old ref in revert commit

Revert
comment references the old one

Revert
a32
2e2
d19'
8b3
Revert
8b3 '

Revert
# Revert a single commit
git revert <ref>

Revert
‣Revert a single change

Revert
# Revert a range of commits
git revert <ref1>..<ref2>

Revert
# Revert a range of commits
git revert <old>..<new>

Revert
must have the old..new refs
in the right order

Amend
amend rewrites the last commit

Amend
‣Amend a bad commit message

Amend
git add <missingfile>
git commit --amend

Amend
‣Amend a missing ﬁle

git-svn
‣Subversion protocol bridge from Git
‣Round-trip integration
‣Transactions in Git == transactions in SVN

git-svn
# Clone one branch
git svn clone <svnurl>

git-svn
# Clone all branches, tags
git svn clone --stdlayout <svnurl>

git-svn
‣Alternate conversion tool
‣ svn2git
‣ https://github.com/nirvdrum/svn2git
‣ Converts tags to Git tags

git-svn
‣Fetch new changes
‣git svn rebase

git-svn
‣Send new changes
‣git svn dcommit

git-svn
‣ SVN Externals
‣ No direct support
‣ Represented as separate repos
‣ Git points at a stable snapshot
‣ SVN Externals follow changes on a branch

git-svn
‣Externals cloning process
‣ svn propget svn:externals <MODULE>
‣ git svn clone --stdlayout <THEURL>
‣ git submodule add <THESUBFOLDER>
‣ git submodule init
‣ git submodule update

git-svn
‣ SVN Externals helper script
‣ https://github.com/andrep/git-svn-clone-externals

@matthewmccull
matthew@github.com
github.com/training

Credits
‣Images sourced from:
‣ AmbientIdeasPhotography.com
‣ Hand Tools
‣ Flickr Creative Commons
‣ Clock: http://www.ﬂickr.com/photos/7729940@N06/4019157830
‣ Wikipedia
‣ Linus Torvalds: http://en.wikipedia.org/wiki/File:Linus_Torvalds.jpeg

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