Ksolis at 07:44, 2 October 2017

2017-10-02T07:44:38Z

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[[Category:course_code_gitusers]]
<slideshow style="nobleprog" headingmark="⌘" incmark="…" scaled="true" font="Trebuchet MS" >
;title: Git - Introduction
;author: David Parkin (NobleProg Ltd)
</slideshow>

== What is Git ⌘==
British Slang
*Variant of get
*A contemptible person, often a fool
*A bastard
[[File:Git-fool.png|300px]]

== Short definition ⌘==

[[File:Git-definitions.png|500px]]

== Why Git? ⌘==
Linus Torvalds has quipped about the name "Git":

"I'm an egotistical bastard, and I name all my projects after myself. First Linux, now git."

[[File:Git-why1.png|264px]] [[File:Git-why2.png]]

== Git History ⌘==
[[File:Git-history.png]]
*2002 - Linux Kernel develops in BitKeeper
*2005 Apr 6 - BitMover drops free license and Linus starts GIT project
*2005 Jun 16 - GIT is officially used to track Linux
*2007 Feb 14 - GIT 1.5.0 is released (more humane)

== Getting Help ⌘==

git commit -h
git help commit
man git-commit

* Git Community Book http://book.git-scm.com/
* Manual (must read) http://www.kernel.org/pub/software/scm/git/docs/user-manual.html
* Git – SVN Crash Course http://git.or.cz/course/svn.html
* Git - CVS Crash Course http://git.or.cz/course/cvs.html

== Git Locally ⌘==
* Git as an extension to the file system
* No network required
* Repository deleted if ''.git'' folder is deleted

== Initializing a repository for existing files ==
git init
git add .
git commit

== Setting Up Username ⌘==
git config --global user.name "Bernard"
git config --global user.email b@noblepog.com

*we can set up config globally - per user
*or for everyone --system

git config --global alias.view "log --oneline --decorate --graph --all"

== Browsing Repository ⌘==
git show rev:file
git show rev:directory
git show rev

== Basic Commands ⌘==
git add file
git rm file
git mv file

== Moving Files ⌘==
git mv afile.txt movedfile.txt

# equivalent to

mv afile.txt movedfile.txt
git rm afile.txt
git add movedfile.txt

== File Status⌘==
https://docs.google.com/drawings/pub?id=1Fp1iYscfMixvIWduFJMejQzmdDmPsvXt3QS3kQ7WSnE&w=800&h=600&.png

== Committing new files and changes ⌘==
# Commiting new files
git add newfile.txt
git commit

# Changes
echo new line >> afile.txt
git add afile.txt
git commit

or

echo new line >> afile.txt
git commit -a

[[File:Git-commit-a1.png|250px]] [[File:Git-commit-a2.png|250px]]

== Committing Folders ⌘==
mkdir afolder
touch afolder/file1.txt
touch afolder/file2.txt
git add afolder
git commit

== Empty Folders ⌘==
mkdir emptyfolder
git add emptyfolder
git commit
# Nothing to commit

#Workaround
touch emptyfolder/.gitignore
git add emptyfolder/.gitignore
git commit
#Worked

== Exercises ⌘==

1. Create a file structure
sudo mkdir /rcs
sudo chmod 777 /rcs
mkdir /rcs/repo
cd /rcs/repo
echo first line > afile.txt
2. Initialize repository

3. Stage the file

4. Check whether the file has been staged

5. Commit the changes

6. Check whether the files have been committed

7. What is the SHA1 of the commit?

== Tracking Changes ⌘==
git status
git diff
git diff rev path
git show

== Diff ⌘==

https://docs.google.com/drawings/pub?id=1_elrohhhWPx8aIqYYZS4D-8Y54VDp_-reloS37NW91A&w=800&h=300&.png

== Diff Examples ⌘==

echo Commited Changes >> afile.txt
git commit -a -m "asdf"

echo Staged Changes >> afile.txt
git add afile.txt

echo Not-tracked Changes >> afile.txt

'''git diff'''
<div class="command-results">
[master c81907a] Commited changes
1 file changed, 1 insertion(+)
diff --git a/afile.txt b/afile.txt
index fc321d0..978da6e 100644
--- a/afile.txt
+++ b/afile.txt
@@ -1,3 +1,4 @@
first line
Commited Changes
Staged Changes
+Not-tracked Changes
</div>

'''git diff --cached'''
<div class="command-results">
diff --git a/afile.txt b/afile.txt
index 37a8835..fc321d0 100644
--- a/afile.txt
+++ b/afile.txt
@@ -1,2 +1,3 @@
first line
Commited Changes
+Staged Changes
</div>

'''git diff HEAD'''
<div class="command-results">
diff --git a/afile.txt b/afile.txt
index 37a8835..978da6e 100644
--- a/afile.txt
+++ b/afile.txt
@@ -1,2 +1,4 @@
first line
Commited Changes
+Staged Changes
+Not-tracked Changes
</div>

'''git diff HEAD^'''
<div class="command-results">
diff --git a/afile.txt b/afile.txt
index 08fe272..978da6e 100644
--- a/afile.txt
+++ b/afile.txt
@@ -1 +1,4 @@
first line
+Commited Changes
+Staged Changes
+Not-tracked Changes
</div>

== Who fixed (spoiled) it? - git annotate ⌘==

'''git annotate afile.txt'''
03be4dec ( Bernard 2012-09-02 14:53:27 +0200 1)first line
c81907a9 ( Bernard 2012-09-02 16:50:24 +0200 2)Commited Changes
00000000 (Not Committed Yet 2012-09-02 17:08:44 +0200 3)Staged Changes
00000000 (Not Committed Yet 2012-09-02 17:08:44 +0200 4)Not-tracked Changes

== Undoing Changes ⌘==
git checkout -- # Remove not staged changes and local copy
git reset HEAD # Remove changes from cache but leaves local copy intact

== Amending latest commit⌘ ==
You can amend your latest commit (re-edit the metadata as well as update the tree)
git commit –amend
To toss your latest commit away completely


== Exercise (Index) ⌘==
# Add the new line to afile.txt
# Check the difference between index and the file
# Add the file
# Check the difference between repository and the staging
# Revert all not committed changes to the file (the file should be the same as in the repo)
# Add new line to a file
# Commit the changes

== Reverting with New Commit ⌘==
Revert the most recent commit:
git revert HEAD
This will create a new commit which undoes the change in HEAD.

Other example:
git revert HEAD^

== Exercise (git revert) ⌘==
# Add the line “bad changes” to afile.txt
# Commit your changes
# Use git revert to remove

== Cleaning Untracked Files ⌘==
touch untrackedfile.txt
git status
echo untrackedfile.txt > .gitignore
git status

git clean -n
git clean -f

== .gitignore syntax ⌘==
Lines starting with '#' are considered comments.
# Ignore any file named foo.txt.
foo.txt
# Ignore (generated) html files,
*.html
# except foo.html which is maintained by hand.
!foo.html
# Ignore objects and archives.
*.[oa]

http://git-scm.com/docs/gitignore

== gitignore vs excludes ⌘==
'''.gitignore'''
* version-controlled
* distributed to other repositories via clone (i.e., files that all developers will want to ignore)
'''$GIT_DIR/info/exclude'''
* specific to a particular repository but which do not need to be shared with other related repositories (e.g., auxiliary files that live inside the repository but are specific to one user’s workflow)
'''~/.gitconfig (core.excludesfile)'''
* ignore in all situations (e.g., backup or temporary files generated by the user’s editor of choice)

== Exercise ⌘==
* echo something > Thumb.db
* Add Thumb.db file to .gitignore
* Add .gitignore to the repository and commit
* Check whether Thumb.db is ignored in afolder
* Clone the repo to /rcs/repoclone
* Check whether the Thumb.db is ignored there

== Browsing Repo ⌘==
gitk
git gui
git log
git show
git show HEAD:afolder
git show HEAD:afile
git show commit (can be tag or branch)
git show HEAD^
git show master
git show c01a0d43

== GIT under the bonnet ⌘==
* Object Database
* SHA1
* DAG (Directed Acyclical Graph)
* Index

== Object Types ⌘==
'''blob'''
*store file data
'''tree'''
*ties one or more "blob" objects into a directory structure
*a tree object can refer to other tree objects, thus creating a directory hierarchy
'''commit'''
*ties such directory hierarchies together into a directed acyclic graph (DAG) of revisions
*each commit contains the object name of exactly one tree (snapshot of the tree)
*a commit refers to "parent" commit objects that describe the history of how we arrived at that directory hierarchy
'''tag'''
*symbolically identifies and can be used to sign other objects
*It contains
**object name (SHA1, e.g. 232A...)
**type of another object
**a symbolic name (e.g. version 1.0.1)
**optionally, a signature (PGP or GPG)

== Directed Acyclic Graph (DAG) ⌘==
{| class="wikitable"
|-
| [[File:Git-dag.png|250px]]
||
*Stored as a '''linked list'''
*Uses SHA1 as references
*One root (object without parents)
*Multiple parents allowed
**merge (2 parents)
**octopus merge (3 or more)
|}

'''DAG and gitk'''

[[File:Git-gitk.png|500px]]

'''DAG and Git objects'''

[[File:Git-dag-git-o.png|350px]]

== Staging Changes ⌘==
[[File:Git-stag-change.PNG|500px]]

== Getting Existing Repo ⌘==
git clone http://git.drupal.org/project/pathauto.git
cd pathauto

'''git remote -v'''
<div class="command-results">
origin http://git.drupal.org/project/pathauto.git (fetch)
origin http://git.drupal.org/project/pathauto.git (push)
</div>

'''git branch -a'''
<div class="command-results">
* 7.x-1.x
remotes/origin/4.6.x-1.x
remotes/origin/4.7.x-1.x
remotes/origin/5.x-1.x
remotes/origin/5.x-2.x
remotes/origin/6.x-1.x
remotes/origin/6.x-2.x
remotes/origin/7.x-1.x
remotes/origin/HEAD -> origin/7.x-1.x
remotes/origin/MAIN
remotes/origin/master
</div>

== Getting new Changes ⌘==
git pull gituser@git.nobleprog.net:/gitrepo/pathauto

== Push Changes to central repo ⌘==
echo Change in readme >> README.txt
git commit -a
git push
git push gituser@git.nobleprog.net:/gitrepo/pathauto

== Adding Remote ⌘==
git remote add central gituser@git.nobleprog.net:/gitrepo/pathauto
git pull central 7.x-1.x
git push central 7.x-1.x

== Exercises ⌘==
#create a bare repository in rcs/main
# Clone bare repo in myrepo
# Modify a file
# Push your changes to main

== Tagging ⌘==
* Tag is not a copy of the repo
* Tag doesn't create a revision
* Tag is just an another name for a revision (apart of SHA1)
git tag tagname # creates tag from HEAD of the current branch
git tag # shows all tags
git tag tagname -m “message”
git tag tagname 6544ce
git tag -l v1

== Lightweight vs Object Tags ⌘==
{| class="wikitable"
|-
! Lightweight !! Object Tags
|-
|
git tag v1.1.0 1b2e1d63n
git push –tags (optional presentation with cloning)
*“a branch that never moves”
*cannot include a comment
*cannot be signed cryptographically
||
git tag -a stable-1 1b2e1d63ff

*If one of -a, -s, or -u <key-id> options is passed
*Needs to contain a message (can be empty)
*can tag any object (not only commit object)
|}

== Exercise (Tagging) ⌘==
* Tag the HEAD as v1.0
*Add another line to a file
echo second line >> afile.txt
*Commit changes
*Tag the commit as v1.1
*Add third line and commit
echo third line >> afile
*Show difference (use git diff) between HEAD and the tag v1.0
*List all the tags

== Branching and Merging ⌘==
git branch
list all branches
git branch <branch>
create a new branch named <branch>, referencing the same point in history as the current branch
git branch <branch> <start-point>
create a new branch named <branch>, referencing <start-point> (branch, tag or commit)
git branch -d <branch>
delete the branch <branch>; if the branch you are deleting points to a commit which is not reachable from the current branch, this command will fail with a warning.
git branch -D <branch>
* forces to do even branch points to a commit not reachable from the current branch
* failed experiment branches
* use only for changes in your repository
git checkout <branch>
switch to the <branch>
git checkout -b <new> <start-point>
create a new branch <new> referencing <start-point>, and check it out

== Dealing with Branches and Tags ⌘==
<source lang = "bash">
git clone git://git.kernel.org/pub/scm/git/git.git
git branch
git branch -r
git tag
git checkout maint
git branch
git checkout v1.7.4
git branch
</source>

== Creating Branches ⌘==
cp repo/ repo.bak -R; cp central/ central.bak -R
Create new branch and switch working copy
git branch experiment
git checkout experiment
git checkout -b experiment

== Merging ⌘==
* switch to experiment
* modify the afile.txt
git commit -a
git checkout master
modify afile.txt (different part)
git commit -a
gitk --all
git branch
git merge experiment
gitk --all

== Exercise (REmoving) ⌘==
# Create branch v2.x
# Modify a couple of files in the branch
# Merge the branch with master
# Remove the branch v2.x

== Exercises (remote branching) ⌘==
* Create a branch “quickfix” from a master branch
git checkout master
git checkout -b quickfix
* create quickfix.txt in quickfix branch and commit
touch quickfix.txt
git add quickfix.txt
git commit -m "quickfix"
* switch to master
git checkout master
* Commit 2 changes into the master branch
echo 1 >> afile.txt; git commit -a -m "change1"
echo 2 >> afile.txt; git commit -a -m "change2"
* switch back to quickfix
git checkout quickfix
* analyse situation in
git log --oneline --decorate --graph --all
* Push the quickfix to the production
push origin quickfix
* On production
git fetch origin quickfix
git branch -a
git checkout origin/quickfix -b quickfix
* On Devel
merge quickfix into master

revert merge

rebase quickfix into master
* delete quickfix branch

== Reverting Merges ⌘==
Adding commit with reverted changes
git revert
Before Committing
git reset --hard HEAD
After Committing
git reset --hard ORIG_HEAD
use only if you committed it only to your private repo

== Rebasing ⌘==
[[File:Git-rebasing1.png|260px]] [[File:Git-rebasing2.png|320px]] [[File:Git-rebasing3.png|320px]]

git checkout -b mywork origin
echo mywork changes >> afile.txt
git commit -a
git checkout master
echo some new func >> afile_master.txt
git add afile_master.txt
git commit
gitk --all
git rebase mywork
gitk --all
git prune
gitk -all

== Exercise ⌘==
# Create a branch “quickfix”
# add a couple of changes afile.txt in quickfix branch
# switch to master
# Commit 2 changes into the master branch
# switch back to quickfix
# analyse situation in gitk --all
# rebase quickfix branch to master
# analyse situation in gitk -all
# prune dangling objects
# gitk --all

== Cherry Picking ⌘==
{| class="wikitable" width="500px"
|-
| [[File:Git-cherry-picking.jpg|250px]]
||
git checkout -b exp
echo Not Cherry1 >> afile.txt
git commit -a -m NotCherry1
echo Cherry >> afile.txt
git commit -a -m Cherry
echo Not Cherry2 >> afile.txt
git commit -a -m NotCherry2
git checkout master
echo masterchange >> afile_master.txt
git add afile_master.txt
git commit -a -m "Master Change"
git log exp
git cherry-pick 3c8f
||
[[File:Git-cherry.png]]
|}

== Stashing ⌘==
* git-stash to save the current state of your work
* git stash save "work in progress for foo feature"
* echo “bug fix” >> afile.txt
* git commit -a -m "fixed the bug"
* git stash pop

== Workflow Structure ⌘==
[[File:Git-wf-structure.png|600px]]

== Combining Commits ⌘==
# Version upto 1.6
git format-patch v1.0..HEAD
git reset v1.0
git apply *.patch
git commit

# Version 1.7 onwords
git reset v1.0
git commit

==Git - Bisect ⌘==
<source lang="bash">
# Initiallize repo
cd /g
mkdir /g/tmp
cd tmp
mkdir repo
cd repo/
git init

echo "exit 0" > code.sh
git add code.sh;
git commit -a -m "c0"

# Genereate 10 revision which do not spoil the script
for i in $(seq 10) ; do echo "# round 1 $i" >> code.sh ; git commit -a -m "c$i" ; done

# Spoil the script
echo "exit 1" > code.sh
git commit -a -m "bug revision"

# generate 20 revisions which do not spoil already spoiled script
for i in $(seq 20) ; do echo "# round 2 $i" >> code.sh ; git commit -a -m "c$i" ; done

git bisect start
git bisect bad
# mark first revision as good
git bisect good 6d34b

git bisect run bash code.sh

</source>

running bash code.sh
Bisecting: 7 revisions left to test after this (roughly 3 steps)
[65e896df0fb1a865e8678bc2145f1621b802acfd] c7
running bash code.sh
Bisecting: 3 revisions left to test after this (roughly 2 steps)
[480515f739bf6dd9a2a6ab47d8626aea805d4880] bug revision
running bash code.sh
Bisecting: 1 revision left to test after this (roughly 1 step)
[52de39416f0f93a1b95f744de05699baa85ab224] c9
running bash code.sh
Bisecting: 0 revisions left to test after this (roughly 0 steps)
[22ef2aaf18c69aa420534303ceeec2078154357c] c10
running bash code.sh
480515f739bf6dd9a2a6ab47d8626aea805d4880 is the first bad commit
commit 480515f739bf6dd9a2a6ab47d8626aea805d4880
Author: Your Name <you@example.com>
Date: Tue Dec 4 00:02:09 2012 +0000

bug revision

:100644 100644 68d815b9ee3a9b590f2be9db2adfe37d715f964f 379a4c986e3265e08e9da42c56ec747619c56a33 M code.sh
bisect run success

Git - David - Revision history

Ksolis at 07:44, 2 October 2017