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Architecture
The basic unit of git is file with a SHA-1 hash, 40 hex characters long, used for the file's name. To prevent file-system issues, git takes the first two characters as a subdirectory and the rest of the hash as the file name. For simplification purpose I'll use a seven character, undivided file name instead. (see git hash-object and git cat-file)
- Blobs: The content. A file of any kind.
- Trees: A text representation of a directory.
- Commits: A text representation of a commit.
A245621
hello, world
B534142
Some other file’s text
In a clever reuse of objects, the representation of a directory, called a tree, is a text file. (see git write-tree)
C534543
A245621 hello.txt
B534142 other.txt
Because the filename is the hash, files with the same content point to the same object, it is the directory text object that holds the different name.
D534544
A245621 hello.txt
B534142 other.txt
B534142 other_copy.txt
Similarly, a commit (or commit-tree) is a text file. It has the hash of the top directory, committer info, commit time and the commit message.
E534535
tree C534543
author First Last <[email protected]> 1243040974 -0700
committer First Last <[email protected]> 1243040974 -0700
commit message
G345807
tree F345346
parent E534535
author First Last <[email protected]> 1243054344 -0700
committer First Last <[email protected]> 1243054344 -0700
second commit message
L345312
tree K534511
parent G345807
parent J345310
author First Last <[email protected]> 1243075625 -0700
committer First Last <[email protected]> 1243075625 -0700
merge commit message
Now we move onto managing this data, these files use a different convention: their name is their file name and what they point to is a text representation of it.
A branch is simply a file. The name of the branch is the name of the file and the contents of the file is the hash (and therefore the filename) of the commit.
refs/heads/master
L345312
The current working branch is stored in the file called HEAD.
HEAD
ref: refs/heads/master
The config file stores configuration information, including remote repository reference information
config example remote entry snippet
[remote "origin"]
url = https://github.com/davious/Test.git
fetch = +refs/heads/*:refs/remotes/origin/*
[branch "master"]
remote = origin
merge = refs/heads/master