Git检出（建立子版本库更新并且合并到master）

HEAD：
head可以理解为“头指针”，是当前工作区的“基础版本”，当执行提交时，HEAD指向的提交将作为新提交的父提交。看看当前HEAD指向。

$ cat .git/HEADref: refs/heads/master

查看master 和 head

$ git rev-parse HEAD master4b9bdcab95d15dd79e7d41c506c9e6e8b1f7c56e4b9bdcab95d15dd79e7d41c506c9e6e8b1f7c56e

此时创建新分支
git checkout -b “myNewBranch”

$ git checkout -b "myNewBranch" Switched to a new branch 'myNewBranch'# rock @ localhost in ~/IdeaProjects/webDemoTwo on git:myNewBranch o [20:34:49] 

会发现当前在分支 myNewBranch 上

$ cat .git/HEADref: refs/heads/myNewBranch

此时修改文件并提交

# rock @ localhost in ~/IdeaProjects/webDemoTwo on git:myNewBranch o [20:34:49] $ git add .# rock @ localhost in ~/IdeaProjects/webDemoTwo on git:myNewBranch x [20:36:39] $ git ci -m "new barnch"[myNewBranch 870ee16] new barnch 1 file changed, 3 insertions(+)

此时查看git 和 master 在哪个提交上

$ git rev-parse HEAD master870ee16a02d07cfddb59d5906cafa48947aafe704b9bdcab95d15dd79e7d41c506c9e6e8b1f7c56e

当前head 在870ee16a02d07cfddb59d5906cafa48947aafe70上；注意将head切换到master上查看log

执行切换：

$ git checkout masterSwitched to branch 'master'Your branch is ahead of 'origin/master' by 4 commits.  (use "git push" to publish your local commits)

查看log

commit 4b9bdcab95d15dd79e7d41c506c9e6e8b1f7c56eAuthor: wangchengwei <[e-mail]>Date:   Tue Nov 28 20:20:48 2017 +0800    测试head和master不在一起的提交commit 049723fa6f1ba44da79d2afd4727356b29bbaa3aAuthor: wangchengwei <[e-mail]>Date:   Tue Nov 28 20:17:02 2017 +0800    test3commit ec4dc0fd08a71f57177b298c8347a97ff646f1a7Author: wangchengwei <[e-mail]>Date:   Mon Nov 27 08:10:06 2017 +0800    重置test2commit 0bfd67bac8a3640bcc70041d7540644a1240cf3dAuthor: wangchengwei <[e-mail]>Date:   Mon Nov 27 08:09:20 2017 +0800    重置test1

并未发现 870ee16a02d07cfddb59d5906cafa48947aafe70的提交。

查看版本库中此id 的log发现在版本库是有这个id的信息

git show 870ee16a02d07cfddb59d5906cafa48947aafe70commit 870ee16a02d07cfddb59d5906cafa48947aafe70Author: wangchengwei <[e-mail]>Date:   Tue Nov 28 20:36:48 2017 +0800    new barnchdiff --git a/firstweb/src/git/git7/TestTwo.java b/firstweb/src/git/git7/TestTwo.javaindex fee886f..deea8b3 100644--- a/firstweb/src/git/git7/TestTwo.java+++ b/firstweb/src/git/git7/TestTwo.java@@ -10,6 +10,9 @@ public class TestTwo {          System.out.printf("重置test4 测试head头");+         System.out.printf("im in new branch");++

而当前head和master在同一id下。此时需要执行merge将这一分支的信息合并到master下。

$ git merge 870ee16a02d07cfddb59d5906cafa48947aafe70Updating 4b9bdca..870ee16Fast-forward firstweb/src/git/git7/TestTwo.java | 3 +++ 1 file changed, 3 insertions(+)

再次查看 head 和master

$ git rev-parse head master870ee16a02d07cfddb59d5906cafa48947aafe70870ee16a02d07cfddb59d5906cafa48947aafe70

此时head和master都指向了这一个提交