如何以编程方式获取git checkout -命令将跳转的目标版本？

Nice question! I’ve run into this exact need before when scripting Git workflows—let’s walk through how to retrieve where git checkout - would take you, without actually updating your current HEAD position.

Background: What git checkout - Actually Does #

First, it’s helpful to know that git checkout - is just a shortcut for checking out the previous working tree location, which Git tracks as @{-1}. This reference points to either a branch name (if you were on a branch before) or a commit hash (if you were in a detached HEAD state).

Step-by-Step Solution #

You can use Git’s built-in rev-parse command to query @{-1} and distinguish between a branch and a detached commit:

1. Check if the previous location is a branch
   Run this command to get the short name of the reference:

   git rev-parse --abbrev-ref @{-1}
   

   • If the output is anything other than HEAD, that’s the branch name git checkout - would switch to.
   • If the output is HEAD, that means your previous state was a detached HEAD, so you’ll need to get the commit ID instead.

2. Get the commit ID for detached HEAD cases
   If the previous step returned HEAD, use this command to get the abbreviated commit hash (or omit --short for the full 40-character hash):

   git rev-parse --short @{-1}
   

Put It All Together in a Script #

For a reusable way to get the target automatically, here’s a simple bash script:

#!/bin/bash

# Get the short reference name of the previous location
prev_location=$(git rev-parse --abbrev-ref @{-1})

if [ "$prev_location" = "HEAD" ]; then
    # Detached HEAD: return abbreviated commit hash
    git rev-parse --short @{-1}
else
    # Branch: return the branch name
    echo "$prev_location"
fi

Notes #

• This relies on Git’s reflog, which is enabled by default for local repositories. If you’ve disabled reflog, this won’t work (but that’s rare for normal use cases).
• @{-1} refers to the immediately previous location—you can also use @{-2} for the one before that, etc., if needed.

内容的提问来源于stack exchange，提问作者jja