22. Inside Git: .Git directory

Goals

  • To learn about Git directory structure.git

01 The .git directory

It is time to do some research. Starting from the project’s root directory...

Run:

ls -C .git

Result:

$ ls -C .git
COMMIT_EDITMSG  MERGE_RR    config      hooks       info        objects     rr-cache
HEAD        ORIG_HEAD   description index       logs        refs

This is a special folder where all the git stuff is. Let us explore the directory.

02 Object Database

Run:

ls -C .git/objects

Result:

$ ls -C .git/objects
09  24  28  45  59  6a  77  80  8c  97  af  c4  e7  info
11  27  43  56  69  6b  78  84  91  9c  b5  e4  fa  pack

You should see a lot of folders named with two characters. The first two letters sha1 hash of the object stored in git are the directory names.

03 inquire the database objects

Run:

ls -C .git/objects/<dir>

Result:

$ ls -C .git/objects/09
6b74c56bfc6b40e754fc0725b8c70b2038b91e  9fb6f9d3a104feb32fcac22354c4d0e8a182c1

Let us look at one of the folders named with two characters. There should be files with names of 38 characters. These files contain objects stored in git. They are compressed and encrypted, so it’s impossible to view their content directly. Let us have a better look at Git directory

04 Config File

Run:

cat .git/config

Result:

$ cat .git/config
[core]
    repositoryformatversion = 0
    filemode = true
    bare = false
    logallrefupdates = true
    ignorecase = true
[user]
    name = Alexander Shvets
    email = alex@githowto.com

This configuration file is created for each individual project. At least in this project, entries in this file will overwrite the entries in the .gitconfig file of your main directory.

05 Branches and tags

Run:

ls .git/refs
ls .git/refs/heads
ls .git/refs/tags
cat .git/refs/tags/v1

Result:

$ ls .git/refs
heads
tags
$ ls .git/refs/heads
master
$ ls .git/refs/tags
v1
v1-beta
$ cat .git/refs/tags/v1
fa3c1411aa09441695a9e645d4371e8d749da1dc

Files in tags subdirectory should be familiar to you. Each file corresponds to the tag previously created using the git tag command. Its content is nothing but a hash commit attached to the tag.

The heads folder is almost identical and is used not for tags, but branches. At the moment we have only one branch, and everything you see in this folder is a master branch.

06 HEAD File

Run:

cat .git/HEAD

Result:

$ cat .git/HEAD
ref: refs/heads/master

There is a reference to the current branch in the HEAD file. At the moment it must be the master branch.