`git merge` 和 `git merge --no-ff` 有什么区别? [英] What is the difference between `git merge` and `git merge --no-ff`?

问题描述

使用 gitk log，我无法发现两者之间的区别.如何观察差异(使用 git 命令或某些工具)?

Using gitk log, I could not spot a difference between the two. How can I observe the difference (with a git command or some tool)?

推荐答案

--no-ff 标志阻止 git merge 执行快进"，如果它检测到您当前的 HEAD 是您尝试合并的提交的祖先.快进是指 git 不构建合并提交，而是将分支指针移动到指向传入提交的位置.这通常发生在没有任何本地更改的 git pull 时.

The --no-ff flag prevents git merge from executing a "fast-forward" if it detects that your current HEAD is an ancestor of the commit you're trying to merge. A fast-forward is when, instead of constructing a merge commit, git just moves your branch pointer to point at the incoming commit. This commonly occurs when doing a git pull without any local changes.

但是，有时您希望防止这种行为发生，通常是因为您想维护特定的分支拓扑(例如，您正在合并一个主题分支，并且希望确保它在阅读历史记录时看起来是这样).为此，您可以传递 --no-ff 标志，git merge 将总是构造一个合并而不是快进.

However, occasionally you want to prevent this behavior from happening, typically because you want to maintain a specific branch topology (e.g. you're merging in a topic branch and you want to ensure it looks that way when reading history). In order to do that, you can pass the --no-ff flag and git merge will always construct a merge instead of fast-forwarding.

同样，如果你想执行一个 git pull 或使用 git merge 来显式快进，如果不能，你想退出快进，然后您可以使用 --ff-only 标志.通过这种方式，您可以不假思索地定期执行诸如 git pull --ff-only 之类的操作，然后如果出现错误，您可以返回并决定是否要合并或变基.

Similarly, if you want to execute a git pull or use git merge in order to explicitly fast-forward, and you want to bail out if it can't fast-forward, then you can use the --ff-only flag. This way you can regularly do something like git pull --ff-only without thinking, and then if it errors out you can go back and decide if you want to merge or rebase.

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