Git merge 的时候，有几种合并方式可以选择

–ff When the merge resolves as a fast-forward, only update the branch pointer, without creating a merge commit. This is the default behavior.

–no-ff Create a merge commit even when the merge resolves as a fast-forward. This is the default behaviour when merging an annotated (and possibly signed) tag.

–squash –no-squash Produce the working tree and index state as if a real merge happened (except for the merge information), but do not actually make a commit, move the HEAD, or record $GIT_DIR/MERGE_HEAD (to cause the next git commit command to create a merge commit). This allows you to create a single commit on top of the current branch whose effect is the same as merging another branch (or more in case of an octopus).

With –no-squash perform the merge and commit the result. This option can be used to override –squash. 而我们平常什么都不加的时候，则使用默认的 –ff ， 即 fast-forward 方式 上图是使用 fast-forward 模式的时候，即 git merge ，这时候 git reset HEAD^ –hard，整个分支会回退到 dev1-commit-3

通常我们把 master 作为主分支，上面存放的都是比较稳定的代码，提交频率也很低，而 develop 是用来开发特性的，上面会存在许多零碎的提交，快进式合并会把 develop 的提交历史混入到 master 中，搅乱 master 的提交历史。所以如果你根本不在意提交历史，也不爱管 master 干不干净，那么 –no-ff 其实没什么用。不过，如果某一次 master 出现了问题，你需要回退到上个版本的时候，比如上例，你就会发现退一个版本到了 commint-3，而不是想要的 commit-2，因为 feature 的历史合并进了 master 里。这也就是很多人都会推荐 –no-ff 的原因了吧。

分支开发注意：

标品和定制品的概念。