如何通过 SHA-1 检查提交是否存在于 Git 存储库中

How to check if the commit exists in a Git repository by its SHA-1

提问by skovalyov

In a similar topic Validate if commit existsthey recommend:

在类似的主题验证是否存在提交中，他们建议：

git rev-list HEAD..$sha

If it exits without error code than the commit exists.

如果它在没有错误代码的情况下退出，则提交存在。

But is it efficient enough just for validation?

但是仅用于验证就足够有效了吗？

I was thinking about this option:

我在考虑这个选项：

git cat-file commit $sha

Is it correct for my task and are there any other ideas?

它对我的任务是否正确，还有其他想法吗？

采纳答案by remram

You can just run git cat-file -t $shaand check it returns "commit". You are right, you don't need to actually print the actual object for that...

您可以运行git cat-file -t $sha并检查它是否返回“提交”。你是对的，你不需要实际打印实际的对象......

I'm not 100% sure that what goes on behind the scene is more efficient, though.

不过，我不能 100% 确定幕后发生的事情更有效。

test $(git cat-file -t $sha) == commit

test $(git cat-file -t $sha) == commit

回答by Paul Draper

git cat-file -e $sha^{commit}

---

---

From git cat-filedocs:

从git cat-file文档：

   -e
      Suppress all output; instead exit with zero status if <object> exists
      and is a valid object.

   -e
      Suppress all output; instead exit with zero status if <object> exists
      and is a valid object.

This (1) shows that this is an intended use case for cat-fileand (2) avoids the resources of actually outputting any commit contents.

这 (1) 表明这是一个预期的用例，cat-file并且 (2) 避免了实际输出任何提交内容的资源。

Appending ^{commit}ensures that the object is a commit (i.e. not a tree or blob) or -- as remram points out -- resolves to a commit.

追加^{commit}确保对象是一个提交（即不是树或 blob）或者——正如 remram 指出的——解析为一个提交。

For example,

例如，

if git cat-file -e $sha^{commit}; then
  echo $sha exists
else
  echo $sha does not exist
fi

回答by andygavin

If you are sure that the sha are commits then cat-file -ecan be used for example:

如果您确定 sha 是提交，则cat-file -e可以使用例如：

if git cat-file -e $sha 2> /dev/null 
then 
  echo exists 
else 
  echo missing 
fi

This is pretty efficient as this is a built-in and doesn't do anything other than checking the sha exists:

这是非常有效的，因为这是一个内置的，除了检查 sha 是否存在之外不做任何事情：

return !has_sha1_file(sha1);

Otherwise if it is uncertain that the sha are commit objects you would need to determine the type as with the other answer using git cat-file -t. This is only slightly less performant as git would have to look at the file information. This isn't as costly as unpacking the whole file.

否则，如果不确定 sha 是提交对象，您将需要使用git cat-file -t. 这只是稍微降低了性能，因为 git 必须查看文件信息。这不像解压整个文件那么昂贵。

回答by Black Mantha

git rev-parse -q --verify "$sha^{commit}" > /dev/null

From the git rev-parsedocs:

从git rev-parse文档：

   --verify
       Verify that exactly one parameter is provided, and that it can be turned into a raw 20-byte SHA-1 that can be used to access the object database. If so, emit it to the standard output; otherwise, error out.

       If you want to make sure that the output actually names an object in your object database and/or can be used as a specific type of object you require, you can add the ^{type} peeling operator to the parameter. For
       example, git rev-parse "$VAR^{commit}" will make sure $VAR names an existing object that is a commit-ish (i.e. a commit, or an annotated tag that points at a commit). To make sure that $VAR names an existing object of
       any type, git rev-parse "$VAR^{object}" can be used.

   -q, --quiet
       Only meaningful in --verify mode. Do not output an error message if the first argument is not a valid object name; instead exit with non-zero status silently. SHA-1s for valid object names are printed to stdout on
       success.

   --verify
       Verify that exactly one parameter is provided, and that it can be turned into a raw 20-byte SHA-1 that can be used to access the object database. If so, emit it to the standard output; otherwise, error out.

       If you want to make sure that the output actually names an object in your object database and/or can be used as a specific type of object you require, you can add the ^{type} peeling operator to the parameter. For
       example, git rev-parse "$VAR^{commit}" will make sure $VAR names an existing object that is a commit-ish (i.e. a commit, or an annotated tag that points at a commit). To make sure that $VAR names an existing object of
       any type, git rev-parse "$VAR^{object}" can be used.

   -q, --quiet
       Only meaningful in --verify mode. Do not output an error message if the first argument is not a valid object name; instead exit with non-zero status silently. SHA-1s for valid object names are printed to stdout on
       success.

As a bonus, if you don't suppress the output, you can get the full sha.

作为奖励，如果你不抑制输出，你可以获得完整的 sha。