GIT

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source: jwiegley.github.io/git-from-the-bottom-up/

 1.Definition of terms

1. Repository
• it is a collection of commits
• it defines HEAD
• it contains a set of branches and tags
2. Index
• changes are first registered in the index
• it is a way of confirming changes before doing a commit
• it is also called the staging area
3. working trees
• it is any directory on your filesystem which has a repository associated with it
• typically indicated by the presence of a sub-directory within-it, named: git
• it includes all the files and subdirectories in that directory
4. Commit
• it is a snapshot of your working tree at some point of time
• it is an archive of what the project`s tree looked like at a past date
• Whether on your machine or someone else`s 
• the state of HEAD at the tim your commit is made becomes that commit`s parent
• this is what creates the notion of a `revision history`
5. branch
• it is just a name for a commit
• it is also called a reference
• it is a parentage of a commit, which defines its history, and thus the typical notopn of a "branch of development"
6. tag
• It is also a name for a commit
• it is similar to a branch
• it always names the same commit (<> branch)
• it can have its own description text
7. master
• it is a branch that is called master
• the mainline of development in most repositoriesis done in master
• This is a typical default, but it is not special
8. head
• it is used by your repository to define what is currently checked out
• you checkout a branch
• HEAD symbolically refers to that branch
• indicating that the branch name should be updated after the next commit operation
• you checkout a specific commit
• HEAD refers to that commit only
• this is referred to as a detached HEAD
• it occurs if you checkout a tag name

2.workflows

• you create a repository
• git checkout
• you complete your work in the working tree
• you complete the bugs
• you are ready to compile
• git-add
• you add your changes to the index
• your changes and all the other are what you intend to commit
• git commit
• you record the content of the index in the repository

REPOSITORY ->git-checkout->WORKING TREE->git-add->INDEX->git-commit->REPOSITORY

3. Repository

File system:

• Root Directory
• directory A (tree)
• file A: leaf node A (blob)
• data1
• data2
• file B:leaf node B
• file C
• dir B
• dir C
• dir D
• ....

4.Blob

1. Create repository
2. Which hash id GIT stores my greetings
• everybodu even in diff computer will get the same hash id
• because GIT realize we track the same content
3. initialize a new repository and commit the file into it
4. Our blob should be in the sys with the hash id as above
• usually six digits: af5626
• or seven af5626k

5.Conclusion

The whole sys is about blob management