我如何唯一标识一个git存储库 [英] How can I uniquely identify a git repository
问题描述
我想创建一个工具，在克隆所述存储库之前检查是否已经有远程存储库的本地克隆。要做到这一点，我需要一种测试方式，如果B是相同的知识库A - 我猜我的意思是他们有可合并的历史。 B可能与A的命名方式不同，并且可能有其他分支 - 通常的用例。
有没有办法做到这一点？我有一个尝试性的想法如何去做，但我想也许这里有人有一个明确的答案。
初步想法
获取分支列表并搜索常见分支（哈希）。然后对于通用分支，检查初始提交是否相同（通过哈希）。那时我会说'够好'。我想我没事，除非有人一直在搞历史，我愿意忽略这种用例。要做到这一点，我需要一种从远程存储库获取分支和提交信息的方式，而不需要做一个克隆。我可以使用ssh& bash，但只有git-only的解决方案才是最好的。
也欢迎对这个不完整的想法提出反馈。
为什么这不是 Git存储库唯一ID
$ b的副本$ b
引用的问题是寻找唯一的存储库ID，或者创建一个。没有这样的野兽存在，即使它存在，在这里它是否有意义也值得怀疑，因为我想确定两个存储库是否具有可合并的历史（即，我可以在两者之间取得和合并） - 一个稍好的定义问题。我愿意忽略用户修改历史记录的可能性，但也希望听到如何处理这种情况。
正如你可以在相关问题中看到的那样; git存储库没有唯一标识。然而;您可以比较主分支上第一次提交的 SHA-1 ;在所有情况下，这应该足够了99.999％（假设第一次提交将永远不会改变）。如果你想更加确定，你可以考虑使用也是第二次提交的SHA-1;再次假设它永远不会改变:)。与前两个提交的SHA-1;我估计你有大概1/2 ^ 320 = 4.7 * 10 ^ -97的机会......
如果你不确定是否有主分支;您可以假设您只有一个无父级root提交，并取其SHA-1。你可以使用这个命令来获得root提交（或提交）：
git rev-list --parents HEAD | egrep^ [a-f0-9] {40} $
（从这个答案）
或者（更容易理解，谢谢@TomHale）：
git rev-list --parents HEAD | tail -1
I would like to create a tool that checks if I already have a local clone of a remote repository before cloning said repository. To do this, I need a way of testing if B is the same as repository A -- by which I guess i mean they have mergeable histories. B might be named differently than A, and might have additional branches -- the usual use cases.
Is there a way to do this? I have a tentative idea how to do it, but I thought perhaps someone here has a definitive answer.
Tentative idea
Get a list of branches and search for common branches (by hash). Then for the common branches, check that the initial commits are the same (by hash). At that point I would say 'good enough'. I figure I'm okay unless someone has been messing with history, which use-case I'm willing to neglect. To do this though, I need a way of getting the branch and commit information from the remote repository, without doing a clone. I can solve this using ssh & bash, but a git-only solution would be preferable.
Feedback on the half-baked idea is also welcome.
Why this is not a duplicate of Git repository unique id
The referenced question is looking for a unique repository id, or a way of creating one. No such beast exists, and even if it did, it is questionable if it would be relevant here, since I want to determine if two repositories have mergeable histories (i.e. I could fetch and merge between the two) -- a slightly better defined problem. I'm willing to ignore the possibilty that a user has modified history, but would love to hear how to handle that case as well.
As you can see in the related question; there is NO unique identification for a git repository. However; you could just compare the SHA-1 of the first commit on the master branch; that should suffice in 99.999% of all cases (supposing that the first commit will never be changed).
And if you want to be even more sure, you could consider using also the SHA-1 of the second commit; again supposing it will never change :). with the SHA-1 of the first two commits; I guess you have about 1 / 2^320 = 4.7*10^-97 chance of being wrong ...
If you are not sure there is even a master branch; you could suppose you have only one parentless root commit, and take its SHA-1. You can use this command to get the root commit (or commits):
git rev-list --parents HEAD | egrep "^[a-f0-9]{40}$"
( copied from this answer)
or (easier to understand, thanks @TomHale):
git rev-list --parents HEAD | tail -1
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