git fetch & git pull

解析.git文件夾

進入正題以前，咱們先來看看.git文件夾

1.config配置文件

[core]

repositoryformatversion = 0
filemode = true
bare = false
logallrefupdates = true
sharedRepository = group

[remote "origin"]

url = https://xxx/xxx/xxx.git
fetch = +refs/heads/*:refs/remotes/origin/*

[branch "master"]

remote = origin
merge = refs/heads/master

配置文件能夠看出
(1).指定本地master分支對應名爲"origin"的遠程庫
(2).名爲"origin"的遠程庫的URL（位置）爲：https://xxx/xxx/xxx.git

2.HEAD文件

ref: refs/heads/issue178

這代表當前分支是issue178，查看當前分支最新<commit>需查看文件 .git/refs/heads/issue178
終端用命令git branch可查看當前所在分支。查看當前分支最新<commit>（即HEAD指向）用命令git log

3.refs文件夾

.git/refs/heads文件夾：保存着本地各個分支的信息
.git/refs/remotes 文件夾：其中每個文件夾表明一個遠程庫名稱（如：origin）

4.logs文件夾

保存的是.git/refs文件夾下相應文件的變動記錄，也就是各個分支變動記錄

git fetch & git pull

1.git fetch：從遠程獲取最新版本到本地，不會自動merge

git checkout issue178
git fetch origin issue178
git log -p issue178..origin/issue178
git merge origin/issue178

解析:
(1).切換到issue178分支
(2).從遠程的origin的issue178主分支下載最新的版本到origin/issue178分支上
(3).比較本地的issue178分支和origin/issue178分支的差異
(4).將origin/issue178分支合併到issue178

上述的另外一種清晰的實現：

git checkout issue178
git fetch origin issue178:test
git diff test
git merge test

解析:
(1).切換到issue178分支
(2).從遠程的origin的issue178主分支下載最新的版本到本地的test分支
(3).比較本地的issue178分支和test分支的差異
(4).將test分支合併到issue178

2.git pull：至關因而從遠程獲取最新版本並merge到本地

git checkout issue178
git pull origin issue178

解析:
等同於上述命令。即git pull至關於git fetch 和 git merge

3.Example

(1) git fetch

git fetch origin issue178:issue178

issue178最新<commit>id：c75abf94ced40ce49e4807fc0b0fb4b2a3dad7f1
origin issue178最新<commit>id：fea9f020b60e9db120395c7ed9c57bd12cd7c085

執行前：
.git/refs/heads/issue178文件內容

c75abf94ced40ce49e4807fc0b0fb4b2a3dad7f1

注：也可查看.git/logs/refs/heads/issue178

.git/refs/remotes/origin/issue178文件內容

c75abf94ced40ce49e4807fc0b0fb4b2a3dad7f1

注：也可查看.git/logs/refs/remotes/origin/issue178

執行後：
.git/refs/heads/issue178文件不變
.git/logs/refs/heads/issue178文件不變

.git/refs/remotes/origin/issue178文件內容變化

fea9f020b60e9db120395c7ed9c57bd12cd7c085

.git/logs/refs/remotes/origin/issue178文件內容變化

(2) git pull

git pull origin issue178:issue178

issue178最新<commit>id：c75abf94ced40ce49e4807fc0b0fb4b2a3dad7f1
origin issue178最新<commit>id：fea9f020b60e9db120395c7ed9c57bd12cd7c085

執行前：
.git/refs/heads/issue178文件內容

c75abf94ced40ce49e4807fc0b0fb4b2a3dad7f1

注：也可查看.git/logs/refs/heads/issue178

.git/refs/remotes/origin/issue178文件內容

c75abf94ced40ce49e4807fc0b0fb4b2a3dad7f1

注：也可查看.git/logs/refs/remotes/origin/issue178

執行後：
.git/refs/heads/issue178文件內容變化

fea9f020b60e9db120395c7ed9c57bd12cd7c085

.git/logs/refs/heads/issue178文件內容變化

.git/refs/remotes/origin/issue178文件內容不變
.git/logs/refs/remotes/origin/issue178文件內容不變

4.圖示