How to git checkout a orgin(unstage) version file in another directoy?

I am writing a script for git-gui's "Tools" menu to diff a file. I want to checkout an origin file in a tmp directory and use the diff tool. Now it is ok to those unstage file,but to those staged file, I found that I do not know how to checkout the orgin(unstage) version.

In detail,I change current directory to a tmp directory,
and use for example 
'git --work-tree=. --git-dir="/media/linux/t/kernel/.git" checkout README'
 to checkout origin version.

Does anyone can help with this? I look the git help and can not find way till now.

Thanks!

Chunlin Zhang venit, vidit, dixit 17.02.2011 08:00:

I'm not sure what you mean by "origin" version, but if you mean the version from the current revision (before making and staging changes), you would check out from HEAD instead of from the index:

git --work-tree=. --git-dir="/media/linux/t/kernel/.git" checkout HEAD -- README

Michael

Michael J Gruber <git <at> drmicha.warpmail.net> writes:

Yes,I mean HEAD version.

It works! Thank you very much!

Michael J Gruber <git <at> drmicha.warpmail.net> writes:

But after I test,I found that after run this command,the file I do checkout action become unstaged. It is weard,because I have set the "--work-tree" to another directory. my command line for example: git --work-tree=. --git-dir="/media/linux/t/kernel/.git" checkout HEAD -- Android.mk

You can test with a git repository.I have no idea how to work around now.

Chunlin Zhang venit, vidit, dixit 17.02.2011 11:17:

So, you don't really want to "checkout" the file. You only want its contents without updating the index. (My brain is apparently too git-rotted already to even think of the possibility that you didn't mean "our checkout" by "checkout").

Jonathan gave you the perfect solution for what you want.

Michael

Michael J Gruber <git <at> drmicha.warpmail.net> writes:

Yes,I am a git newbie,a little bit misunderstanding about the git-checkout.

Anyway,your answer make me more familiar about git cli usage.

Michael J Gruber <git@drmicha.warpmail.net> writes:

Wouldn't that still affect the index in /media/linux/t/kernel/.git/index, making /media/linux/t/kernel/README and the index entry out-of-sync?

Junio C Hamano venit, vidit, dixit 17.02.2011 19:33:

Yes. I guess you overlooked the two posts where Chunlin and I realised that I took his request for "checkout" too giterally.

Michael

Chunlin Zhang wrote:

Because you are writing a script, I'd suggest using one of the "low-level commands (plumbing)" listed in git(1). Because you are retrieving a file, it would be one of the "interrogation commands". And because it is a single file, I suppose this should be git cat-file, git unpack-file, or git archive.

For example,

	git cat-file blob HEAD:README

will print the contents of README in the HEAD commit.

Because I am curious: what exactly would your script be used to do? Can the git diff-tree or git diff-files command help?

Jonathan Nieder <jrnieder <at> gmail.com> writes:

Wow,this solved my problem perfectly. use this command for example: git --work-tree=. --git-dir="/media/linux/t/kernel/.git" cat-file blob HEAD:Android.mk>Android.mk

Thanks !

Chunlin Zhang <zhangchunlin@gmail.com> writes:

You won't need --work-tree any more, since cat-file only looks at the object database.

Andreas.