git学习 分支管理(3)：分支管理策略——禁用Fast forward模式（分支图）（第七天）
文章目录
- 分支管理策略
-
- 禁用Fast forward模式
- Fast forward模式
- 开发原则
分支管理策略
通常，合并分支时，如果可能，Git会用Fast forward模式，但这种模式下，删除分支后，会丢掉分支信息。
如果要强制禁用Fast forward模式，Git就会在merge时生成一个新的commit，这样，从分支历史上就可以看出分支信息。
禁用Fast forward模式
下面我们实战一下–no-ff 方式的 git merge ：
首先，仍然创建并切换dev分支：
$ git switch -c dev
Switched to a new branch 'dev'
修改readme.txt文件，并提交一个新的commit：
asus@XXX MINGW64 /e/Git_warehouse (dev)
$ git status
On branch dev
Changes not staged for commit:
(use "git add ..." to update what will be committed)
(use "git restore ..." to discard changes in working directory)
modified: readme.txt
no changes added to commit (use "git add" and/or "git commit -a")
asus@XXX MINGW64 /e/Git_warehouse (dev)
$ git add readme.txt
asus@XXX MINGW64 /e/Git_warehouse (dev)
$ git status
On branch dev
Changes to be committed:
(use "git restore --staged ..." to unstage)
modified: readme.txt
asus@XXX MINGW64 /e/Git_warehouse (dev)
$ git commit -m "add merge"
[dev fa1517e] add merge
1 file changed, 1 insertion(+)
asus@XXX MINGW64 /e/Git_warehouse (dev)
$ git status
On branch dev
nothing to commit, working tree clean
之所以列出菜鸟的，是为了提醒大家千万要 git status ！
现在，我们切换回master：
$ git switch master
Switched to branch 'master'
Your branch is ahead of 'origin/master' by 3 commits.
(use "git push" to publish your local commits)
注意：这里出现后面的
Your branch is ahead of ‘origin/master’ by 3 commits.
(use “git push” to publish your local commits)
是因为菜鸟和GitHub仓库有3次版本的跨度，而且这里后面还会用到，读者（没一起跟菜鸟学习的）可能不会出现，也不必纠结这个！
准备合并dev分支，请注意–no-ff参数，表示禁用Fast forward：
$ git merge --no-ff -m "merge with no-ff" dev
Merge made by the 'recursive' strategy.
readme.txt | 1 +
1 file changed, 1 insertion(+)
注意：正如最上面说的，如果要强制禁用Fast forward模式，Git就会在merge时生成一个新的commit，所以才要加上-m，把commit描述写进去。
合并后，我们用 git log --graph 看看分支历史：
$ git log --graph
* commit 8002fa2e223018c9858685f96966bfc1f8fc3250 (HEAD -> master)
|\ Merge: adc26a9 fa1517e
| | Author: ****
| | Date: Sun Jul 12 17:34:02 2020 +0800
| |
| | merge with no-ff
| |
| * commit fa1517e0bd07a65542bf7736c64ba3585a4cff0d (dev)
|/ Author: ****
| Date: Sun Jul 12 17:32:45 2020 +0800
|
| add merge
|
* commit adc26a9c79012f0def89aeb3362e0155de69655a
|\ Merge: 6edf4c3 2809b02
| | Author: ****
| | Date: Sat Jul 11 16:10:20 2020 +0800
| |
| | conflict fixed
可以看到，不使用Fast forward模式，merge后就像这样：
那么删除分支后会有什么改变吗？
$ git branch -d dev
Deleted branch dev (was fa1517e).
注意：was fa1517e是缩写的版本号，读者的肯定和我不一样！
再次，用 git log --graph 看看分支历史：
$ git log --graph
* commit 8002fa2e223018c9858685f96966bfc1f8fc3250 (HEAD -> master)
|\ Merge: adc26a9 fa1517e
| | Author: ****
| | Date: Sun Jul 12 17:34:02 2020 +0800
| |
| | merge with no-ff
| |
| * commit fa1517e0bd07a65542bf7736c64ba3585a4cff0d
|/ Author: ****
| Date: Sun Jul 12 17:32:45 2020 +0800
|
| add merge
|
* commit adc26a9c79012f0def89aeb3362e0155de69655a
|\ Merge: 6edf4c3 2809b02
| | Author: ****
| | Date: Sat Jul 11 16:10:20 2020 +0800
| |
| | conflict fixed
发现没有变化！
想想也是，删除的只是分支的指针，自然不会对log产生什么影响！
然后 git status ，结果如下：
On branch master
Your branch is ahead of 'origin/master' by 5 commits.
(use "git push" to publish your local commits)
nothing to commit, working tree clean
发现版本差距从3变成了5，git log 就可以发现：
$ git log
commit 8002fa2e223018c9858685f96966bfc1f8fc3250 (HEAD -> master)
Merge: adc26a9 fa1517e
Author: ****
Date: Sun Jul 12 17:34:02 2020 +0800
merge with no-ff
commit fa1517e0bd07a65542bf7736c64ba3585a4cff0d
Author: ****
Date: Sun Jul 12 17:32:45 2020 +0800
add merge
commit adc26a9c79012f0def89aeb3362e0155de69655a
Merge: 6edf4c3 2809b02
Author: ****
Date: Sat Jul 11 16:10:20 2020 +0800
conflict fixed
多的两个版本正好一个是自己commit的，一个就是禁用Fast forward模式而产生的！
Fast forward模式
例如：
$ git switch -c dev
Switched to a new branch 'dev'
asus@XXX MINGW64 /e/Git_warehouse (dev)
$ git branch
* dev
master
asus@XXX MINGW64 /e/Git_warehouse (dev)
$ git status
On branch dev
$ e "git add ..." to update what will be committed)
(use "git restore ..." to discard changes in working directory)
modified: readme.txt
no changes added to commit (use "git add" and/or "git commit -a")
asus@XXX MINGW64 /e/Git_warehouse (dev)
$ git add readme.txt
asus@XXX MINGW64 /e/Git_warehouse (dev)
$ git status
On branch dev
Changes to be committed:
(use "git restore --staged ..." to unstage)
modified: readme.txt
asus@XXX MINGW64 /e/Git_warehouse (dev)
$ git commit -m "add merge2"
[dev 4165a59] add merge2
1 file changed, 1 insertion(+), 1 deletion(-)
asus@XXX MINGW64 /e/Git_warehouse (dev)
$ git status
On branch dev
nothing to commit, working tree clean
asus@XXX MINGW64 /e/Git_warehouse (dev)
$ git switch master
Switched to branch 'master'
Your branch is ahead of 'origin/master' by 5 commits.
(use "git push" to publish your local commits)
asus@XXX MINGW64 /e/Git_warehouse (master)
$ git merge dev
Updating 8002fa2..4165a59
Fast-forward
readme.txt | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
asus@XXX MINGW64 /e/Git_warehouse (master)
$ git log --graph
* commit 4165a59cf8e4d6434f81231481fbb099141d0741 (HEAD -> master, dev)
| Author: ****
| Date: Sun Jul 12 17:38:45 2020 +0800
|
| add merge2
|
* commit 8002fa2e223018c9858685f96966bfc1f8fc3250
|\ Merge: adc26a9 fa1517e
| | Author: ****
| | Date: Sun Jul 12 17:34:02 2020 +0800
| |
| | merge with no-ff
| |
| * commit fa1517e0bd07a65542bf7736c64ba3585a4cff0d
|/ Author: ****
| Date: Sun Jul 12 17:32:45 2020 +0800
|
| add merge
asus@XXX MINGW64 /e/Git_warehouse (master)
$ git branch -d dev
Deleted branch dev (was 4165a59).
asus@XXX MINGW64 /e/Git_warehouse (master)
$ git log --graph
* commit 4165a59cf8e4d6434f81231481fbb099141d0741 (HEAD -> master)
| Author: ****
| Date: Sun Jul 12 17:38:45 2020 +0800
|
| add merge2
|
* commit 8002fa2e223018c9858685f96966bfc1f8fc3250
|\ Merge: adc26a9 fa1517e
| | Author: ****
| | Date: Sun Jul 12 17:34:02 2020 +0800
| |
| | merge with no-ff
| |
| * commit fa1517e0bd07a65542bf7736c64ba3585a4cff0d
|/ Author: ****
| Date: Sun Jul 12 17:32:45 2020 +0800
|
| add merge
|
asus@XXX MINGW64 /e/Git_warehouse (master)
$ git status
On branch master
Your branch is ahead of 'origin/master' by 6 commits.
(use "git push" to publish your local commits)
nothing to commit, working tree clean
可以很轻易地发现，Fast forward模式下，分支不会被展示！而且commit也只进行了一个，所以版本只由5变成了6！
所以还是建议使用上面的一种（禁用Fast forward模式），不然没有记录是一件很令人头疼的事，而且也不直观！
开发原则
首先，master分支应该是非常稳定的，也就是仅用来发布新版本，平时不能在上面干活；
那在哪干活呢？干活都在dev分支上，也就是说，dev分支是不稳定的，到某个时候，比如1.0版本发布时，再把dev分支合并到master上，在master分支发布1.0版本；
你和你的小伙伴们每个人都在dev分支上干活，每个人都有自己的分支，时不时地往dev分支上合并就可以了。
所以，团队合作的分支看起来就像这样：
这里最下面两条相当于你工作的分支，dev是开发分支（你和你的同事都提交到这个分支上），master是主分支！