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Git

Git#

Intro#

What?#

Why?#

  1. As a collaboration tool
  2. As a version control tool

Terminologies#

master#

origin#

remote#

url#

Setup & Config#

config#

CRLF, LF, CR#

Windows Only#
  • Then turn off automatical convertions, and stick to CRLF only
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git config --global core.autocrlf false
Linux/Mac Only#
  • If on LF system, then do this to convert any CRLF to LF
  • but not LF to CRLF
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git config --global core.autocrlf input
If Both#
  • Then set this in Windows system only
    • auto-converting CRLF line endings into LF when you add a file to the index
    • and vice versa when it checks out code onto your filesystem
    • hence Git will be having LF but windows filesystem will always have CRLF
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git config --global core.autocrlf true

Inspection & Comparision#

diff#

Compare local with remote branch#

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git diff <masterbranch_path> <remotebranch_path>

#or 

git diff master origin/master

diff-tree#

List all the files in a commit#

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git diff-tree --no-commit-id --name-only -r bd61ad98

show#

List all the files in a commit#

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git show --pretty="" --name-only bd61ad98

Commands#

init#

--bare#

  • Source: http://www.saintsjd.com/2011/01/what-is-a-bare-git-repository/

clone#

  • Normal Way git clone url:repo

  • Clone a specific release git clone url:repo --branch <tag#>

pull#

  • git pull origin master
  • git pull origin master -f
  • git pull --rebase origin master

add#

rm#

commit#

  • commit -m "message"
  • commit --amend
    • to re-phrase the commit message; iff commit has not been pushed

push#

checkout#

status#

log#

To see in descriptive format

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git log --graph --decorate --oneline

where:
--graph: shows flow
--decorate: shows branch names
--oneline: compact description in single line

reflog#

To see in short

reset#

Uses#

Branching#

  • Lets say you have 2 branches:
    • master
    • dev

  • Options:

    • create a new branch dev 
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      git checkout -b dev
    • dev is active 
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      git checkout dev
    • master is active 
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      git checkout master
    • dev is active & incorporate master in it 
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      git checkout dev
git merge master

    • master is active & incorporate dev in it 

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      git checkout master
git merge dev

    • delete a local branch if completely merged 

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      git branch -d dev

    • delete a local branch if not merged 

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      git branch -D dev

    • delete a remote branch 

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      git push origin :dev

    • Rename your local branch.

      • If you are on the branch you want to rename: 
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        git branch -m new-name
      • If you are on a different branch: 
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        git branch -m old-name new-name

    • Delete the old-name remote branch and push the new-name local branch. 

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      git push origin :old-name new-name

    • Reset the upstream branch for the new-name local branch.

      • Switch to the branch and then: 
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        git push origin -u new-name

  • Golden rules

    • first incorporate master into dev
    • check compatibility/bugs/conflicts & resolve them
    • now incorporate/merge dev in master

Merging#

merge Vs rebase#

  1. Both are used for same purpose but with different approach
  2. Integrates changes from one branch to another

merge#

  • Lets say, if you're woring on a feature in a dedicated branch. And someone makes a commit in master branch and you want to pull those changes to your feature branch, i.e.
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      A---B---C feature
     /
D---E---F---G master

here A,B,C are commits in feature. F,G are new commits in master

then:

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git checkout feature
git merge master
Or in one line 
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git merge master feature
This will create a new commit in feature branch called as "merge commit" and feature branch will have same history as master (but not vice-versa) i.e. 
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      A---B---C---(*) feature
     /           /
D---E---F---G---H master

here (*) is merge commit

  • Very active master branch can pollute the feature branch.

rebase:#

  • Alternative to merging
  • rebases feature branch onto master branch
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git checkout feature
git rebase master

shifts the entire feature branch to tip/(latest node) of the master branch. i.e.

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               A'--B'--C' feature
             /
D---E---F---G master

here A',B',C' are brand new commits
  • instead of creating "merge commit", it creates brand new commits in feature branch for all the commits created earlier on the feature branch (the changes will same, but with new commit infos)
  • i.e. re-writes branch history
  • Benifits over merge
    • gives cleaner history log by avoiding un-necessary "merge commits"
    • results in perfectly linear project history

Golden rules to use rebase: * never use rebase on any public branch: Means, don't rebase the master branch onto feature branch (it is opposite of rebasing feature branch onto master branch). It will create a brand new commit/history in master branch which will affect other developers.

rebase one branch on the top of another#

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         Branch-1   Branch-2
         X--Y     A--B--C 
        /        /
D---E---F---G---H   master


After rebaseing Branch-1 on the top of Branch-2

         A--B--C--X--Y   Branch-1
        /    
         A--B--C         Branch-2
        /       
D---E---F---G---H        master

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git checkout branch1
git rebase branch2

Reverting back to old commits#

https://stackoverflow.com/questions/4114095/how-to-revert-a-git-repository-to-a-previous-commit

Reseting#

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git checkout <branch>

git reflog

pick the commit_sha one prior to the the incident

git reset --hard <commit_sha>

--hard    Matches the working tree and index to that of the tree being
               switched  to. Any changes to tracked files in the working tree since
               <commit> are lost.




git reset --merge <commit_sha>
or 
git reset --merge <head_count>

--merge       Resets the index to match the tree recorded by the named commit, and
              updates the files that are different between the named commit and
              the current commit in the working tree.

Modify last commit Message#

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git commit -a -m

Modify a particular commit#

If you want to modify files at commit 

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git rebase -i <SHA>

You will get a editor opened up with list of all the commits prior to that.

Change the pick to edit for that particular commit . Save & close the editor.

Make changes to your files.

After that add or rm files.

If you want to change the commit msg also then

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git commit -a

Then continue rebasing

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git rebase --continue

Squashing last x commits into one#

If you want to squash last X commits into single commit then

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git rebase -i HEAD~X

You will get a editor opened up with list of all the X commits.

Change the pick to s for all the commits except the oldest one into which you want to merge all the lastest.

Save & close the editor.

Again you'll get an editor with list & order of all the squashed commits. (if you want you can change the commit msgs at this moment)

Then continue rebasing

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git rebase --continue

Done.

Misc#

Travis CI (Continue Integration)#

Continuous Integration is the practice of merging in small code changes frequently - rather than merging in a large change at the end of a development cycle. The goal is to build healthier software by developing and testing in smaller increments.

Prerequisites#

To start using Travis CI, make sure you have all of the following:

  • GitHub login
  • Project hosted as a repository on GitHub
  • Working code in your project
  • Working build or test script

Steps to Integrate CI#

  • Using github login to
  • Enable the repo in CI portal

  • Add .travis.yml file to the repo to tell Travis CI what to do

    • e.g. ```yaml

    language: python python: - "3.6.4"

    command to install dependencies#

    install: # - pip install -r requirements.pip - pip install pipenv - "pipenv install --dev"

    command to run tests#

    script: # - pytest src/test.py # or py.test for Python versions 3.5 and below - pipenv run pytest src/test.py # or py.test for Python versions 3.5 and below ```

  • Infrastructure options
    ```yaml

    os: linux

    dist: trusty

    sudo: enabled

    ```

  • Add the .travis.yml file to git, commit and push, to trigger a Travis CI build

    • Travis only runs builds on the commits you push after you’ve enabled the repository in Travis CI.
  • check the build page
  • embbed build status on github page

Setup SSH key#

Generate or Get ssh key#

Generate#
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ssh-keygen
Set paraphrase#
Get#
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ls ~/.ssh

Add the key to the ssh-agent#

Start#
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eval `ssh-agent`
Add#

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ssh-add ~/.ssh/<private_key_file>
where is generally id_rsa

Provide paraphrase#

Add the public key to your VCS portal settings#

Copy hash of public key#
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cat ~/.ssh/id_rsa.pub

or

xclip -sel clip ~/.ssh/id_rsa.pub
Paste in settings#
Update remotes with ssh url#
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git remote rm origin

git remote add origin [email protected]:toransahu/ethereal-machines-backend.git