如何将 HEAD 移回以前的位置?(分离头) &撤消提交 [英] How can I move HEAD back to a previous location? (Detached head) & Undo commits

问题描述

在 Git 中，我试图通过合并另一个分支然后通过以下方式将 HEAD 重置到前一个位置来执行 squash commit:

git reset origin/master

但我需要走出这一步.如何将 HEAD 移回之前的位置?

我有提交的 SHA-1 片段 (23b6772)，我需要将其移动到.我怎样才能回到这个提交?

解决方案

在回答之前，先来补充一下背景，解释一下这个HEAD是什么.

首先什么是 HEAD?

HEAD 只是对当前分支上的当前提交(最新)的引用.
在任何给定时间只能有一个 HEAD(不包括 git worktree).

HEAD 的内容存储在 .git/HEAD 中，它包含当前提交的 40 字节 SHA-1.

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分离的 HEAD

如果您不是最新提交 - 这意味着 HEAD 指向历史记录中的先前提交，则称为 分离的 HEAD.

在命令行上，它看起来像这样 - SHA-1 而不是分支名称，因为 HEAD 没有指向当前分支的尖端:

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关于如何从分离的 HEAD 中恢复的几个选项:

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In Git, I was trying to do a squash commit by merging in another branch and then resetting HEAD to the previous place via:

git reset origin/master

But I need to step out of this. How can I move HEAD back to the previous location?

I have the SHA-1 fragment (23b6772) of the commit that I need to move it to. How can I get back to this commit?

解决方案

Before answering, let's add some background, explaining what this HEAD is.

First of all what is HEAD?

HEAD is simply a reference to the current commit (latest) on the current branch.
There can only be a single HEAD at any given time (excluding git worktree).

The content of HEAD is stored inside .git/HEAD and it contains the 40 bytes SHA-1 of the current commit.

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detached HEAD

If you are not on the latest commit - meaning that HEAD is pointing to a prior commit in history it's called detached HEAD.

On the command line, it will look like this - SHA-1 instead of the branch name since the HEAD is not pointing to the tip of the current branch:

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A few options on how to recover from a detached HEAD:

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git checkout

git checkout <commit_id>
git checkout -b <new branch> <commit_id>
git checkout HEAD~X // x is the number of commits to go back

This will checkout the new branch pointing to the desired commit.
This command will checkout to a given commit.
At this point, you can create a branch and start to work from this point on.

# Checkout a given commit.
# Doing so will result in a `detached HEAD` which mean that the `HEAD`
# is not pointing to the latest so you will need to checkout branch
# in order to be able to update the code.
git checkout <commit-id>

# Create a new branch forked to the given commit
git checkout -b <branch name>

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git reflog

You can always use the reflog as well.
git reflog will display any change which updated the HEAD and checking out the desired reflog entry will set the HEAD back to this commit.

Every time the HEAD is modified there will be a new entry in the reflog

git reflog
git checkout HEAD@{...}

This will get you back to your desired commit

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git reset --hard <commit_id>

"Move" your HEAD back to the desired commit.

# This will destroy any local modifications.
# Don't do it if you have uncommitted work you want to keep.
git reset --hard 0d1d7fc32

# Alternatively, if there's work to keep:
git stash
git reset --hard 0d1d7fc32
git stash pop
# This saves the modifications, then reapplies that patch after resetting.
# You could get merge conflicts if you've modified things which were
# changed since the commit you reset to.

• Note: (Since Git 2.7) you can also use the git rebase --no-autostash as well.

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git revert <sha-1>

"Undo" the given commit or commit range.
The reset command will "undo" any changes made in the given commit.
A new commit with the undo patch will be committed while the original commit will remain in history as well.

# Add a new commit with the undo of the original one.
# The <sha-1> can be any commit(s) or commit range
git revert <sha-1>

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This schema illustrates which command does what.
As you can see there, reset && checkout modify the HEAD.

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