重新合并以更改合并提交的父级 [英] Rebasing to change parent of a merge commit
问题描述
D 只是恢复 C （这意味着工作目录在 B 和 D中相同）。 A --- B --- C --- D主人
\\
E --- F --- G功能
我想添加 C 及其在 F 中的合并之前的历史 D 到历史记录中，如下所示：
A --- B --- C --- D主人
\\
E ----------- F' - G'功能
I don'我想要改变 E （这实际上是一系列长时间的提交）。
git rebase --onto DB （如建议此处）导致合并冲突（有或没有 - preserve-merges ）。
有没有办法实现我想要的？
大多数方法都会有点痛苦。使用 git filter-branch 有一个中等无痛苦的版本，除了filter-branch本身很痛苦。 :-)（你可以过滤提交 F 和 G 并编写一个提交过滤器，用于替换新父项你需要 F'，并让filter-branch操作替换 G 。）
我认为不使用低级命令的最简单的方法就是进行新的合并，然后将 G 转换为新合并。新合并可能会有冲突，但我们并不在意，我们只想采用旧合并的树，我们可以这样做：
$ git checkout< sha1> ＃在这里使用D或E的sha-1。
＃请注意：无论您使用何种方式，
＃都是我们新的
＃merge的第一个父级;基于此选择。
$ git merge --no-commit< sha1> ＃在这里使用剩余的sha-1
[忽略结果内容]
$ git rm -rf。 ＃注意：假设你在工作树顶部目录
$ git checkout< sha1-of-F> - 。
$ git commit＃创建合并提交F'
第一个 checkout 让你在一个SHA-1的分离HEAD上， merge --no-commit 启动与另一个SHA-1的合并过程， git rm -rf。会抛出合并树和任何冲突，并且 git checkout< id> - 。填充上一次合并的索引和工作树。最后一个 git commit 创建合并 F'与merge F ，但与父母不同。
此时（仍然使用分离的HEAD），您可以重新绑定（或选择）提交 G （或许多提交 G ），然后强制您的分支指向新图形的顶端。我建议使用 git rebase ... --onto HEAD 但我没有用分离的HEAD测试过，至少有一种方法可能会出错（解决 HEAD 给一个ID太晚了）。
低级 git commit-tree 命令实际上可能更简单。 Andrew C在评论中写了正确的命令，尽管你必须用 git update-ref 来说明分支名称。
使用更熟悉的命令的好处在于它们更熟悉。
Suppose I've got the following history, where the top line is the master branch, the lower one is a feature branch that's merged with master at one point, and D just reverts C (which means that the working directory is the same in B and D).
A---B---C---D master
\ \
E---F---G feature
I want to add C and its reversion D to the history before the merge in F, like this:
A---B---C---D master
\ \
E-----------F'--G' feature
I don't want to change E (which is actually a long series of commits).
git rebase --onto D B (as suggested here) results in merge conflicts (with or without --preserve-merges).
Is there a way to accomplish what I want?
Most methods will be somewhat painful. There's a moderately painless version using git filter-branch, except that filter-branch itself is painful. :-) (You'd filter commits F and G and write a commit-filter that substitutes in the new parents you want for F', and let the filter-branch operation replace the parentage for G.)
I think the simplest method that does not resort to low level commands is just to make a new merge, then rebase G onto the new merge. The new merge may have conflicts but we don't care, we just want to take the old merge's tree, which we can do like this:
$ git checkout <sha1> # Use D or E's sha-1 here.
# Note: whichever you use will
# be the first parent of our new
# merge; choose based on that.
$ git merge --no-commit <sha1> # use the remaining sha-1 here
[ignore resulting stuff]
$ git rm -rf . # Note: assumes you're in top dir of work tree
$ git checkout <sha1-of-F> -- .
$ git commit # Create merge commit F'
The first checkout gets you on a detached HEAD with one SHA-1, the merge --no-commit starts the merge process with the other SHA-1, the git rm -rf . throws away the merged tree and any conflicts, and the git checkout <id> -- . fills in the index and work-tree from the previous merge. The final git commit creates merge F' with the same tree as merge F, but with different parents.
At this point (still with a detached HEAD) you can rebase (or cherry-pick) commit G (or many commits G), then force your branch to point to the tip of the new graph. I'd suggest using git rebase ... --onto HEAD but I have not tested this with a detached HEAD and there's at least one way it might go wrong (resolving HEAD to an ID too late).
The low level git commit-tree command may actually be even simpler. Andrew C wrote the correct command in a comment, although you have to spell out the branch name with git update-ref. [Edit: maybe not quite correct, the two parents you want are D and E, not D and B. Again, put the one you want as first-parent first.]
The advantage (?) of using the more familiar commands is that they're, well, more familiar.
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