本文主要介绍一些我在日常开发中与Git分支相关的一些操作，通过实例阐述一些基本分支概念
分支的本质 Git分支的本质仅仅只是指向Commit对象的可变指针
master分支并非一个特殊分支
Merge Fast-Forward Merge 当前分支（HEAD）指向的Commit对象是待被合并分支所指向Commit对象的**上游**，只需要简单地向前移动HEAD指针
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 $ git log --oneline --decorate --graph --all * c4292f7 (hotfix) C4 | * bebf901 (dev) C3 |/ * b17415c (HEAD -> master) C2 * 425fa18 C1 * 1f62295 C0 $ git merge hotfix Updating b17415c..c4292f7 Fast-forward C4 | 0 1 file changed, 0 insertions(+), 0 deletions(-) create mode 100644 C4 $ git log --oneline --decorate --graph --all * c4292f7 (HEAD -> master, hotfix) C4 # Master just move forward to hotfix | * bebf901 (dev) C3 |/ * b17415c C2 * 425fa18 C1 * 1f62295 C0
Recursive Merge 非上游时，寻找最近共同祖先，做三方合并，新建一个Commit对象
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 $ git log --oneline --decorate --graph --all * be69c83 (dev) C5 * bebf901 C3 | * c4292f7 (HEAD -> master) C4 # Merge dev , can not be fast forward |/ * b17415c C2 * 425fa18 C1 * 1f62295 C0 $ git merge dev -m 'M1' Merge made by the 'recursive' strategy. # Recursive merge , create new commit object M1 C3 | 0 C5 | 0 2 files changed, 0 insertions(+), 0 deletions(-) create mode 100644 C3 create mode 100644 C5 $ git log --oneline --decorate --graph --all * 3226137 (HEAD -> master) M1 |\ | * be69c83 (dev) C5 | * bebf901 C3 * | c4292f7 C4 |/ * b17415c C2 * 425fa18 C1 * 1f62295 C0
Remote Branch
origin与master一样，并无特殊含义，仅仅是Git的默认名称
origin origin：Remote Repository的引用origin/master：Remote Branch的引用master：Local Branch的引用
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 $ git clone https://github.com/hzmajia/demo.git Cloning into 'demo'... remote: Counting objects: 3, done. remote: Total 3 (delta 0), reused 3 (delta 0), pack-reused 0 Unpacking objects: 100% (3/3), done. Checking connectivity... done. $ gst On branch master Your branch is up-to-date with 'origin/master'. # master auto track origin/master nothing to commit, working directory clean $ git log --decorate --graph --oneline * 7118626 (HEAD -> master, origin/master, origin/HEAD) Add README.md $ cn=C1 && touch $cn && git add . && git commit -m $cn # master move forward [master 0b2eae6] C1 1 file changed, 0 insertions(+), 0 deletions(-) create mode 100644 C1 $ gst On branch master Your branch is ahead of 'origin/master' by 1 commit. # master track origin/master (use "git push" to publish your local commits) nothing to commit, working directory clean $ git log --decorate --graph --oneline * 0b2eae6 (HEAD -> master) C1 * 7118626 (origin/master, origin/HEAD) Add README.md
git fetch
git fetch仅仅抓取Remote Repository的数据到本地数据库(包括移动相关指针），但并不会自动合并数据
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 $ git remote -v # Show remote repository repA https://github.com/hzmajia/repA.git (fetch) repA https://github.com/hzmajia/repA.git (push) repB https://github.com/hzmajia/repB.git (fetch) repB https://github.com/hzmajia/repB.git (push) $ git log --decorate --graph --oneline * 4f8de53 (HEAD -> master, repB/master, repA/master) C1 # All up-to-date By Now * 51ce03d C0 $ git fetch repA remote: Counting objects: 2, done. remote: Compressing objects: 100% (2/2), done. remote: Total 2 (delta 0), reused 2 (delta 0), pack-reused 0 Unpacking objects: 100% (2/2), done. From https://github.com/hzmajia/repA 4f8de53..262e1d5 master -> repA/master $ git log --decorate --graph --oneline --all * 262e1d5 (repA/master) C3 # Move forward , repA/master , local read only * 4f8de53 (HEAD -> master, repB/master) C1 * 51ce03d C0 $ git fetch repB remote: Counting objects: 2, done. remote: Compressing objects: 100% (2/2), done. remote: Total 2 (delta 0), reused 2 (delta 0), pack-reused 0 Unpacking objects: 100% (2/2), done. From https://github.com/hzmajia/repB 4f8de53..54824f8 master -> repB/master $ git log --decorate --graph --oneline --all * 54824f8 (repB/master) C4 # Move forward , repB/master , local read only | * 262e1d5 (repA/master) C3 |/ * 4f8de53 (HEAD -> master) C1 * 51ce03d C0
track remote branch
本地分支可以跟踪远程分支，被跟踪的远程分支是本地分支的上游分支（upstream branch）
git clone master自动跟踪repo_name/master
1 2 3 4 5 6 7 8 9 10 $ git clone https://github.com/hzmajia/repA.git Cloning into 'repA'... remote: Counting objects: 7, done. remote: Compressing objects: 100% (5/5), done. remote: Total 7 (delta 1), reused 6 (delta 0), pack-reused 0 Unpacking objects: 100% (7/7), done. Checking connectivity... done. $ git branch -vv # Show upstream branch * master 262e1d5 [origin/master] C3
git checkout -b：从远程分支创建新分支，分支名自定义，并跟踪该远程分支--track：从远程分支创建新分支，分支名与远程分支一致，并跟踪该远程分支
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 $ git remote -v origin https://github.com/hzmajia/repA.git (fetch) origin https://github.com/hzmajia/repA.git (push) $ git checkout -b branchA origin/master # branchA track origin/master Branch branchA set up to track remote branch master from origin. Switched to a new branch 'branchA' $ git branch -vv * branchA 262e1d5 [origin/master] C3 master 262e1d5 [origin/master] C3 $ git checkout --track origin/dev # dev track origin/dev Branch dev set up to track remote branch dev from origin. Switched to a new branch 'dev' $ git branch -vv branchA 262e1d5 [origin/master] C3 * dev 262e1d5 [origin/dev] C3 master 262e1d5 [origin/master] C3
git brach -u -u：修改当前分支的跟踪分支（上游分支）
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 $ gst On branch dev Your branch is up-to-date with 'origin/dev'. nothing to commit, working directory clean $ git branch -vv branchA 262e1d5 [origin/master] C3 * dev 262e1d5 [origin/dev] C3 master 262e1d5 [origin/master] C3 $ git branch -u origin/master # update upstream branch Branch dev set up to track remote branch master from origin. $ git branch -vv branchA 262e1d5 [origin/master] C3 * dev 262e1d5 [origin/master] C3 master 262e1d5 [origin/master] C3
git pull
查找当前分支的上游分支，从远程仓库拉取数据并尝试合并，推荐使用**git fetch+git merge**
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 $ git branch -vv * master 7e00be3 [origin/master] C6 $ git branch test $ git branch -vv * master 7e00be3 [origin/master] C6 test 7e00be3 C6 $ git remote -v origin https://github.com/hzmajia/repA.git (fetch) origin https://github.com/hzmajia/repA.git (push) $ git log --oneline --graph --decorate --all * 7e00be3 (HEAD -> master, origin/master, origin/HEAD, test) C6 * 8a1ed87 C5 * 262e1d5 (origin/dev) C3 * 4f8de53 C1 * 51ce03d C0 $ git pull remote: Counting objects: 2, done. # Fetch data remote: Compressing objects: 100% (1/1), done. remote: Total 2 (delta 1), reused 2 (delta 1), pack-reused 0 Unpacking objects: 100% (2/2), done. From https://github.com/hzmajia/repA 7e00be3..ae121e2 master -> origin/master Updating 7e00be3..ae121e2 # Master auto merge origin/master , test do nothing Fast-forward C7 | 0 1 file changed, 0 insertions(+), 0 deletions(-) create mode 100644 C7 $ git log --oneline --graph --decorate --all * ae121e2 (HEAD -> master, origin/master, origin/HEAD) C7 * 7e00be3 (test) C6 * 8a1ed87 C5 * 262e1d5 (origin/dev) C3 * 4f8de53 C1 * 51ce03d C0
Rebase
谨慎使用，适用于尚未push的Commit，rebase会丢弃现有Commit，新建Commit，从而使得提交历史更加整洁，我在实际开发中比较少使用，真实记录开发中的提交历史
原理 A rebase B：寻找两者的最近共同祖先C，将C到A的一系列Commit按次序应用到B上，生成一系列新的Commit，对应的Commit Message不变
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 $ git log --oneline --graph --decorate --all * 360950a (HEAD -> master) C6 * 7567dc8 C5 | * 7dd1dde (dev) C4 | * 72fec7e C3 |/ * b77035b C2 * 8e4fa74 C1 * e43aa3d C0 $ git rebase dev # create new commit objects 8e15506 0ed259f First, rewinding head to replay your work on top of it... Applying: C5 Applying: C6 $ git log --oneline --graph --decorate --all * 0ed259f (HEAD -> master) C6 # 360950a...0ed259f * 8e15506 C5 # 7567dc8...8e15506 * 7dd1dde (dev) C4 * 72fec7e C3 * b77035b C2 * 8e4fa74 C1 * e43aa3d C0
错误样例
下例中因为对已push的Commit进行rebase，产生了两个C4，令人很疑惑。这是因为rebase默认生成新的Commit，但Commit Message是一致的
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 57 58 59 60 61 62 63 64 65 66 67 $ git log --oneline --graph --decorate --all * b91c74e (HEAD -> master) C6 |\ | * 35cc8be (dev) C5 * | e196df0 C4 |/ * 0e127f0 (origin/master) C1 $ git push origin master Counting objects: 6, done. Compressing objects: 100% (6/6), done. Writing objects: 100% (6/6), 545 bytes | 0 bytes/s, done. Total 6 (delta 2), reused 0 (delta 0) remote: Resolving deltas: 100% (2/2), done. To https://github.com/hzmajia/demo.git 0e127f0..b91c74e master -> master $ git log --oneline --graph --decorate --all * b91c74e (HEAD -> master, origin/master) C6 |\ | * 35cc8be (dev) C5 * | e196df0 C4 |/ * 0e127f0 C1 $ git reset --hard HEAD^ HEAD is now at e196df0 C4 $ git log --oneline --graph --decorate --all * b91c74e (origin/master) C6 |\ | * 35cc8be (dev) C5 * | e196df0 (HEAD -> master) C4 |/ * 0e127f0 C1 $ git rebase dev # rebase pushed commit , generate 2 C4 in log !!! First, rewinding head to replay your work on top of it... Applying: C4 $ git log --oneline --graph --decorate --all * 4a785d4 (HEAD -> master) C4 | * b91c74e (origin/master) C6 | |\ | |/ |/| * | 35cc8be (dev) C5 | * e196df0 C4 |/ * 0e127f0 C1 $ git pull Merge made by the 'recursive' strategy. $ git log --oneline --graph --decorate --all * a6637b9 (HEAD -> master) Merge branch 'master' of https://github.com/hzmajia/demo |\ | * b91c74e (origin/master) C6 | |\ | * | e196df0 C4 * | | 4a785d4 C4 | |/ |/| * | 35cc8be (dev) C5 |/ * 0e127f0 C1
