本文主要介绍合并中断，查看冲突，冲突相关的提交，撤销合并

中断合并

git merge --abort：当出现冲突时，放弃当前合并，尝试恢复到合并前的状态

$ git branch -v
  dev    43b3f7b echo dev > file
* master 3f112d7 echo master > file

$ git diff dev # conflict exists
diff --git a/file b/file
index 38f8e88..1f7391f 100644
--- a/file
+++ b/file
@@ -1 +1 @@
-dev
+master

$ git merge dev
Auto-merging file
CONFLICT (content): Merge conflict in file
Automatic merge failed; fix conflicts and then commit the result.

$ gst
On branch master
You have unmerged paths.
  (fix conflicts and run "git commit")
Unmerged paths:
  (use "git add <file>..." to mark resolution)
    both modified:   file
no changes added to commit (use "git add" and/or "git commit -a")

$ git merge --abort

$ gst
On branch master
nothing to commit, working directory clean

查看冲突

git ls-files -u：显示unmerged的文件，有三个版本
- Stage 1：共同的祖先版本
- Stage 2：自身版本
- Stage 3：MERGE_HEAD版本（将要被合并的版本）
git diff --base：等效于git diff
git diff --ours：突出ours，等效于git diff HEAD
git diff --theirs：突出theirs，等效于git diff MERGE_HEAD

$ git branch -v
  dev    43b3f7b echo dev > file
* master 3f112d7 echo master > file

$ git merge dev
Auto-merging file
CONFLICT (content): Merge conflict in file
Automatic merge failed; fix conflicts and then commit the result.

$ gst -sb
## master
UU file

$ git ls-files -u
100644 e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 1 file
100644 1f7391f92b6a3792204e07e99f71f643cc35e7e1 2 file
100644 38f8e886e1a6d733aa9bfa7282568f83c133ecd6 3 file

$ git show :1:file

$ git show :2:file
master

$ git show :3:file
dev

$ git diff --base
* Unmerged path file
diff --git a/file b/file
index e69de29..0010ca6 100644
--- a/file
+++ b/file
@@ -0,0 +1,5 @@
+<<<<<<< HEAD
+master
+=======
+dev
+>>>>>>> dev

$ git diff --ours
* Unmerged path file
diff --git a/file b/file
index 1f7391f..0010ca6 100644
--- a/file
+++ b/file
@@ -1 +1,5 @@
+<<<<<<< HEAD
 master # highlight
+=======
+dev
+>>>>>>> dev

$ git diff --theirs
* Unmerged path file
diff --git a/file b/file
index 38f8e88..0010ca6 100644
--- a/file
+++ b/file
@@ -1 +1,5 @@
+<<<<<<< HEAD
+master
+=======
 dev # highlight
+>>>>>>> dev

冲突来源

git log --merge：显示与冲突相关的提交

$ git log --oneline --decorate --graph --all
* f14595d (HEAD -> master) add c.txt
* b69a9be echo master > a.txt
| * 4ffcc97 (dev) add b.txt
| * 6f197c8 echo dev > a.txt
|/
* 51c144f add a.txt

$ git log --oneline --left-right master...dev # see 「Git++ - 引用和提交区间」
< f14595d add c.txt
< b69a9be echo master > a.txt
> 4ffcc97 add b.txt
> 6f197c8 echo dev > a.txt

$ git diff master..dev # conflict exists
diff --git a/a.txt b/a.txt
index 1f7391f..38f8e88 100644
--- a/a.txt
+++ b/a.txt
@@ -1 +1 @@
-master
+dev
diff --git a/b.txt b/b.txt
new file mode 100644
index 0000000..e69de29
diff --git a/c.txt b/c.txt
deleted file mode 100644
index e69de29..0000000

$ git merge dev
Auto-merging a.txt
CONFLICT (content): Merge conflict in a.txt
Recorded preimage for 'a.txt'
Automatic merge failed; fix conflicts and then commit the result.

$ git log --left-right --oneline --merge -p
< b69a9be echo master > a.txt
diff --git a/a.txt b/a.txt
index e69de29..1f7391f 100644
--- a/a.txt
+++ b/a.txt
@@ -0,0 +1 @@
+master
> 6f197c8 echo dev > a.txt
diff --git a/a.txt b/a.txt
index e69de29..38f8e88 100644
--- a/a.txt
+++ b/a.txt
@@ -0,0 +1 @@
+dev

撤销合并

将要介绍reset和revert这两种方式来撤销已提交的合并，请谨慎使用，适用于尚未共享的提交

reset `--hard`

相关内容请参照「Git++ - Reset」

$ git log --oneline --decorate --graph --all
*   7a18228 (HEAD -> master) M1
|\
| * c446a31 (dev) C3
| * 8e12eb6 C2
* | bc8551b C5
* | 220958f C4
|/
* 4d8ef47 C1
* 0c1d26b C0

$ git reset --hard HEAD~
HEAD is now at bc8551b C5

$ git log --oneline --decorate --graph --all
* bc8551b (HEAD -> master) C5
* 220958f C4
| * c446a31 (dev) C3
| * 8e12eb6 C2
|/
* 4d8ef47 C1
* 0c1d26b C0

revert

当提交对象是普通提交对象C1时，新建提交对象C2，还原C1的修改
当提交对象是合并提交对象是C1，新建提交对象C2，保留其中一个父提交对象P1，还原其他父提交对象的修改
revert后再次merge，有可能出现Already up-to-date，因为在当前提交对象能回溯到相关的提交。如果想再次合并之前放弃掉的父提交对象的修改，可以再次执行revert或直接reset --hard

revert -m：保留父提交对象，1代表第一父提交对象，2代表第二提交对象

$ git log --oneline --decorate --graph --all
*   f16d507 (HEAD -> master) M1
|\
| * c446a31 (dev) C3
| * 8e12eb6 C2
* | bc8551b C5
* | 220958f C4
|/
* 4d8ef47 C1
* 0c1d26b C0

$ ls
C0  C1  C4  C5

$ git revert -m 1 HEAD # keep C5 , give up C3
[master bc96ef3] Revert "M1" -m 1
 2 files changed, 0 insertions(+), 0 deletions(-)
 delete mode 100644 C2
 delete mode 100644 C3

$ git log --oneline --decorate --graph --all
* bc96ef3 (HEAD -> master) Revert "M1" -m 1
*   f16d507 M1
|\
| * c446a31 (dev) C3
| * 8e12eb6 C2
* | bc8551b C5
* | 220958f C4
|/
* 4d8ef47 C1
* 0c1d26b C0

$ ls # as same as C5
C0  C1  C4  C5

$ git merge dev # can track C2 C3
Already up-to-date.

dev上新增提交C6，master merge dev不会出现C2和C3，因为本质是bc96ef3 merge 105cf17

$ git checkout dev
Switched to branch 'dev'

$ cn=C6 && touch $cn && git add . && git commit -m $cn
[dev 105cf17] C6
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 C6

$ git checkout master
Switched to branch 'master'

$ git merge dev -m 'M2'
Merge made by the 'recursive' strategy.
 C6 | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 C6

$ git log --oneline --decorate --graph --all
*   f58ffc1 (HEAD -> master) M2
|\
| * 105cf17 (dev) C6
* | bc96ef3 Revert "M1" -m 1
* |   f16d507 M1
|\ \
| |/
| * c446a31 C3
| * 8e12eb6 C2
* | bc8551b C5
* | 220958f C4
|/
* 4d8ef47 C1
* 0c1d26b C0

$ ls # C2 C3 lost!!
C0  C1  C4  C5  C6

如果想再次复现C2和C3的修改，可以revert bc96ef3或者reset --hard f16d507，注意这些提交对象应该都是没有被共享的

$ git reset --hard HEAD^^
HEAD is now at f16d507 M1

$ git merge dev -m 'M2'
Merge made by the 'recursive' strategy.
 C6 | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 C6

$ git log --oneline --decorate --graph --all
*   ea0507c (HEAD -> master) M2
|\
| * 105cf17 (dev) C6
* |   f16d507 M1
|\ \
| |/
| * c446a31 C3
| * 8e12eb6 C2
* | bc8551b C5
* | 220958f C4
|/
* 4d8ef47 C1
* 0c1d26b C0

$ ls
C0  C1  C2  C3  C4  C5  C6