git

• alias

  alias gitlog='git log --all --decorate --oneline --graph'
  

• stash
  helps you stash your work away and clear your working directory. Then when you checkout it will not carry over the new code with you.
  refer

  git stash               # add them to the stash
  git pull                # do update
  git stash pop           # get the changes back into your working tree
  

• reset
  reset works with refs, on your working directory and the index, without touching any commit objects (or other objects)

  git reset --hard
  git reset 
  

• rebase
  Rebasing a branch in Git is a way to move the entirety of a branch to another point in the tree and rewrite previously made commit objects.

        /o-----o---o--o-----o--------- branch
  --o-o--A--o---o---o---o----o--o-o-o--- master
  after rebase
                                   /o-----o---o--o-----o------ branch
  --o-o--A--o---o---o---o----o--o-o-o master
  

• rebase interactive

  git rebase -i HEAD~5
  git rebase --continue
  drop/squash...
  

• squash
  a way to rewrite your commit history

• rebase and merge
  rebase branch b1 on to current master, means take branch b1(from commit 7f3b00e to commit 872a38f) and rebase (put them on top of) master (60dc441).

 $ git log --oneline --graph --all
 * 60dc441 (HEAD -> master) adding master.txt file
 | * 872a38f (b1) adding b1 file
 |/
 * 7f3b00e adding file 2
 * df2fb7a adding file 1

 $ git checkout b1
 Switched to branch 'b1'

 # Rebase (b1 which is current branch) on master
 $ git rebase master
 First, rewinding head to replay your work on top of it...
 Applying: adding b1 file

 # The result
 $ git log --oneline --graph --all
 * 5372c8f (HEAD -> b1) adding b1 file
 * 60dc441 (master) adding master.txt file
 * 7f3b00e adding file 2
 * df2fb7a adding file 1

 $ git checkout master
 Switched to branch 'master'

 # the current history, where b1 is based on master
 $ git log --oneline --graph --all
 * 5372c8f (b1) adding b1 file
 * 60dc441 (HEAD -> master) adding master.txt file
 * 7f3b00e adding file 2
 * df2fb7a adding file 1


 # Performing the merge, notice the "fast-forward" message
 $ git merge b1
 Updating 60dc441..5372c8f
 Fast-forward
 b1.txt | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 b1.txt

 # The Result
 $ git log --oneline --graph --all
 * 5372c8f (HEAD -> master, b1) adding b1 file
 * 60dc441 adding master.txt file
 * 7f3b00e adding file 2
 * df2fb7a adding file 1

refer

• merge

  git checkout feature
  git merge master
     /o--o--o--o---------- feature
  --o--o--o--o--master------ /
  

  This will create a new “Merge commit” in the feature branch that holds the history of both branches.

  <<<<<<< HEAD
  current
  =======
  need to be merged
  >>>>>>> updated_address
  

• another branch

  git checkout -b new_local_branch SHA
  git pull upstream/remote_branch
  

• cherrypick
  if you want to make a pr to branch A by cherry-picking a commit from a branch B
  ```
  # to get the latest branches
  git pull –rebase upstream branchA

git checkout branchA

git cherry-pick #even if the commit is on a different branch (e.g. master)

# to push the commit
git push origin branchA

- resolve conflicts
0. git fetch origin master # run in the local personal branch
1. git rebase origin/master # in local personal branch , rebase your branch on top of the latest master branch
2. edit files to resolve conflicts

«< HEAD –> latest change from master
====

xxx -> my local changes
```

1. git add
2. git rebase –continue
3. git log
4. git push -f origin

• cherry pick
  refer

git checkout master
git cherry-pick xxx

refer

Object
All the information needed to represent the history of a project is stored in files referenced by a 40-digit “object name” that looks something like this:
6ff87c4664981e4397625791c8ea3bbb5f2279a3

Every object consists of three things - a type, a size and content. The size is simply the size of the contents, the contents depend on what type of object it is, and there are four different types of objects: “blob”, “tree”, “commit”, and “tag”.

A “blob” is used to store file data - it is generally a file.
A “tree” is basically like a directory - it references a bunch of other trees and/or blobs (i.e. files and sub-directories)
A “commit” points to a single tree, marking it as what the project looked like at a certain point in time. It contains meta-information about that point in time, such as a timestamp, the author of the changes since the last commit, a pointer to the previous commit(s), etc.
A “tag” is a way to mark a specific commit as special in some way. It is normally used to tag certain commits as specific releases or something along those lines.

git show <SHA>
git ls-tree <SHA>

Multiple accounts
refer

 ssh-keygen -t rsa -C "email@work_mail.com" -f "id_rsa_work_user1"
 ssh-add ~/.ssh/id_rsa_work_user1

 ~/.ssh/config

 ## config
 git config --global url."ssh://git@xxx".insteadOf "https://xxx"

 # Work account-1
 Host github.com-work_user1    
    HostName github.com
    User git
    IdentityFile ~/.ssh/id_rsa_work_user1