.git directory acts a major role in git VCS. We can do local verson management directly depended on .git directory. I will parse .git in current topic.
Directory tree First, I created a project and managed it through git, its directory tree is as follows:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 . ├── doc │ └── README.md ├── .git │ ├── COMMIT_EDITMSG │ ├── config │ ├── description │ ├── HEAD │ ├── hooks │ │ ├── applypatch-msg.sample │ │ ├── commit-msg.sample │ │ ├── fsmonitor-watchman.sample │ │ ├── post-update.sample │ │ ├── pre-applypatch.sample │ │ ├── pre-commit.sample │ │ ├── prepare-commit-msg.sample │ │ ├── pre-push.sample │ │ ├── pre-rebase.sample │ │ ├── pre-receive.sample │ │ └── update.sample │ ├── index │ ├── info │ │ └── exclude │ ├── logs │ │ ├── HEAD │ │ └── refs │ │ └── heads │ │ ├── dev │ │ ├── dev-1.0 │ │ └── master │ ├── objects │ │ ├── 02 │ │ │ ├── 40351d75b3f451e0ec4b399c38c3758f007152 │ │ │ └── d8eae705ebf203142fd2f381d3b216dde2b28f | | |... │ │ ├── c8 │ │ │ └── ff9c55ce2651d8380a14bee5b43b37e14fa7fc │ │ ├── f0 │ │ │ └── 45488f3fa9a350ac01f48f2b000fe51a53f5aa │ │ ├── info │ │ └── pack │ ├── ORIG_HEAD │ └── refs │ ├── heads │ │ ├── dev │ │ ├── dev-1.0 │ │ └── master │ └── tags │ └── kikoff_tag ├── img │ └── check.png ├── lib │ └── css_practice_1.html ├── README.md └── src └── README.md
.git introduction .git/HEAD It indicates which branch or commit the project works on. When the project works on a branch, the valuse of .git/HEAD is one reference. The details are as follows:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 $ cat .git/HEAD ref: refs/heads/dev-1.0 $ git checkout master Switched to branch 'master' $ cat .git/HEAD ref: refs/heads/master $ git checkout 8c19a3856 Note: checking out '8c19a38' . ... HEAD is now at 8c19a38 Add Copyright notice. $ cat .git/HEAD 8c19a3856e27ff8e29171e49ccccdc042f1de32e
.git/config .git/config is local git configuration,it has the highest priority, it will cover global and system configuration. As follows:
1 2 3 4 5 6 7 8 9 10 11 12 $ cat .git/config [core] repositoryformatversion = 0 filemode = false bare = false logallrefupdates = true symlinks = false ignorecase = true [user] name = lihq0416 email = lihq0416@alsa.com
My global configuration is as follows:
1 2 3 E:\code\Git\Demonstration>git config --global --list user.name=huaqianlee user.email=huaqianlee@gmail.com
The working configuration(user) is as follows:
1 2 3 4 5 6 7 $ git log -n1 commit 8c19a3856e27ff8e29171e49ccccdc042f1de32e (HEAD -> master) Author: lihq0416 <lihq0416@alsa.com> Date: Sun Mar 8 11:14:06 2020 +0800 Add Copyright notice.
.git/refs/ .git/refs/ saves git reference, it replaces SHA-1 with a simple string.
1 2 3 4 5 $ ls .git/refs/ heads/ tags/ heads - branch HEAD tags - milestone, tag reference
index Git puts the file size, creation time, and last modification information in the index.
Git judges whether the blob has changed by comparing the current status with the content of index.
.git/refs/heads/ .git/refs/heads saves all branch name, as follows:
1 2 $ ls .git/refs/heads/ dev dev-1.0 master
we can get the original SHA-1 value by cat.
1 2 3 4 5 6 7 8 9 10 11 12 $ cat .git/refs/heads/master 1ff08f245a3eaae8c5404cf3da2977a4637d3d68 $ git cat-file -t 1ff08f2 commit $ cat .git/refs/heads/dev 1134f9ee07daf1589ec9cc424dec587d119f8477 $ cat .git/refs/heads/dev-1.0 2cb23acda7fc092152fd63c5c13bda287765d9da
Check the content .git/refs/heads/master.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 $ git cat-file -p 1ff08f2 tree ccb86ecb23a86d363868ede3f8597dade731aeac parent 8c19a3856e27ff8e29171e49ccccdc042f1de32e author lihq0416 <lihq0416@alsa.com> 1583640484 +0800 committer lihq0416 <lihq0416@alsa.com> 1583640484 +0800 Modify README.md. $ git show 1ff08f2 commit 1ff08f245a3eaae8c5404cf3da2977a4637d3d68 (HEAD -> master) Author: lihq0416 <lihq0416@alsa.com> Date: Sun Mar 8 12:08:04 2020 +0800 Modify README.md. diff --git a/README.md b/README.md index a687b4c..401b9a8 100644 --- a/README.md +++ b/README.md @@ -1,3 +1,3 @@ Demonstration === - +For master.
The SHA-1 in .git/refs/heads is the HEAD pointer of every branch.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 $ git log --oneline --all --graph * 1134f9e (dev) Make graph more readability * 71c40d3 Modify README.md in dev branch. | * 1ff08f2 (HEAD -> master) Modify README.md. | * 8c19a38 Add Copyright notice. | * 318c11a Copy css to lib. |/ * ce4297f Add image. | * 2cb23ac (dev-1.0) README for dev-1.0 branch. |/ * 6fc4b44 (tag: kikoff_tag) Copy doc README.md * 726c6c0 Add source README.md * c8ff9c5 Add README $ git branch -av dev 1134f9e Make graph more readability dev-1.0 2cb23ac README for dev-1.0 branch. * master 1ff08f2 Modify README.md.
.git/refs/tags save all tags, next, we analyze the tag reference.
1 2 $ cat .git/refs/tags/kikoff_tag 6fc4b448eede8b86e0dff1156797a8b76b661c98
Again, let’s look at the details of the tag object.
1 2 3 4 5 6 7 8 9 10 $ git cat-file -t 6fc4b44 commit $ git cat-file -p 6fc4b44 tree e38a164f48baba5a6b6251d77926be66e77ae1c0 parent 726c6c01c5bdfee5c477962f69f5313d868398db author lihq0416 <lihq0416@alsa.com> 1583636454 +0800 committer lihq0416 <lihq0416@alsa.com> 1583636454 +0800 Copy doc README.md
it is the SHA-1 of kikoff_tag tag.
.git/objects .git/objects saves all git objects.
1 2 3 4 5 6 7 8 9 10 11 $ ls -l .git/objects/ total 0 drwxr-xr-x 1 Lee 197121 0 三月 8 11:45 02/ drwxr-xr-x 1 Lee 197121 0 三月 8 12:10 11/ ... drwxr-xr-x 1 Lee 197121 0 三月 7 18:20 c8/ drwxr-xr-x 1 Lee 197121 0 三月 8 11:45 dd / drwxr-xr-x 1 Lee 197121 0 三月 8 11:00 e3/ drwxr-xr-x 1 Lee 197121 0 三月 7 18:16 info/ drwxr-xr-x 1 Lee 197121 0 三月 7 18:16 pack/
List the contens of c8/ and dd/, the content appends path name to the SHA-1.
1 2 3 4 5 6 $ ls -l .git/objects/c8/ total 1 -r--r--r-- 1 Lee 197121 132 三月 7 18:20 ff9c55ce2651d8380a14bee5b43b37e14fa7fc $ ls .git/objects/dd/ 5ab753d33087eb06bd69b3a9317674638e6685 9f4c82726240a5289b5e6e33028bbcee8ac540
Cat the contents of SHA-1.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 1. c8/ directory $ git cat-file -t c8ff9c55 commit $ git cat-file -p c8ff9c55 tree 567fa4f607ea3685f7957cf42d1569ada65eb53b author lihq0416 <lihq0416@alsa.com> 1583576427 +0800 committer lihq0416 <lihq0416@alsa.com> 1583576427 +0800 Add README 2. dd / directory $ git cat-file -t dd5ab753 tree $ git cat-file -p dd5ab753 100644 blob 9bdec0343dd1dee61d37be2a4d678c1a43c20b69 README.md $ git cat-file -t 9bdec0343 blob $ git cat-file -p 9bdec0343 Hello, source code! $ git cat-file -t dd9f4c82 blob $ git cat-file -p dd9f4c82 Demonstration === For dev-1.0.
There are mainly three objects:
tree : indicates a directory.
commit : indicates a commit(SHA-1).
blob: indicates a file, if the contents of two files are same, they saves as a same blob.
More in .git # Todo
1 2 config FETCH_HEAD hooks/ info/ objects/ packed-refs description HEAD index logs/ ORIG_HEAD refs/
commit, tree and blob commit, tree and blob are three main components of .git. I will introduce them by two examples.
The current commit history is as follows:
1 2 3 4 5 6 7 8 9 10 $ git log --oneline 5ea3cec (HEAD -> master) Modify README.md of src 2b6e826 Same file, same blob 1ff08f2 Modify README.md. 8c19a38 Add Copyright notice. 318c11a Copy css to lib. ce4297f Add image. 6fc4b44 (tag: kikoff_tag) Copy doc README.md 726c6c0 Add source README.md c8ff9c5 Add README
Simple one First, list relationship flowchart.
1 2 3 4 5 6 7 8 9 10 $ git cat-file -t 726c6c0 commit $ git cat-file -p 726c6c0 tree c72f3764e2179a8c61f0b948aca0b3720624b818 parent c8ff9c55ce2651d8380a14bee5b43b37e14fa7fc author lihq0416 <lihq0416@alsa.com> 1583636339 +0800 committer lihq0416 <lihq0416@alsa.com> 1583636339 +0800 Add source README.md
Get the content of tree object.
1 2 3 $ git cat-file -p c72f3764 100644 blob a687b4c895de1b963fd4648cd12d7b1040b406c0 README.md 040000 tree dd5ab753d33087eb06bd69b3a9317674638e6685 src
100644 - blob; 040000 - tree
Get the contents of blob and tree.
1 2 3 4 5 6 7 8 9 $ git cat-file -p a687b4c Demonstration === $ git cat-file -p dd5ab75 100644 blob 9bdec0343dd1dee61d37be2a4d678c1a43c20b69 README.md $ git cat-file -p 9bdec03 Hello, source code!
Complex one First, list the relationship flowchart too.
1 2 3 4 5 6 7 $ git cat-file -p 5ea3cec tree eda5671a377d2fcd258cfabbe13d0eaaff59a69a parent 2b6e8269574c910b51492ce4c6731a1820b8b5da author lihq0416 <lihq0416@alsa.com> 1583652333 +0800 committer lihq0416 <lihq0416@alsa.com> 1583652333 +0800 Modify README.md of src
1 2 3 4 5 6 $ git cat-file -p eda567 100644 blob 401b9a8be1ba5ce77df18d4038a58dbfa29e3122 README.md 040000 tree 04a87dd49ac3c928b872613bb07e8545ba08493a doc 040000 tree bd5e80e9c3527d86ffdf7669521082ec282043d9 img 040000 tree b2713206c3d2f15dd71b25d124189edd2e8beab8 lib 040000 tree 8a55fe88f7a7129f5467d791e4f077c22c3b3bbd src
