Howto update a 'dirty' entry in the cache from the object database

Howto update a 'dirty' entry in the cache from the object database

[Thomas Glanzmann]

Hello,
I edited a bunch of files and notice that I want to revert back one of
the files to the original one (the one that comes with HEAD). But I
already updated the cache. Is there a way to 'patch' the cache with the
original file. Or do I need todo a read-tree into a temporary index
file. Check out the one file from this alternate index file and use
update-cache to update my original index file?

	Thomas [ who want's a "git revert" ]

Re: Howto update a 'dirty' entry in the cache from the object database

[Linus Torvalds]

On Wed, 4 May 2005, Thomas Glanzmann wrote:
>
> I edited a bunch of files and notice that I want to revert back one of
> the files to the original one (the one that comes with HEAD). But I
> already updated the cache. Is there a way to 'patch' the cache with the
> original file.

Absolutely.

You can do it several ways. The easiest one is

	git-read-tree -m HEAD
	git-checkout-cache -f filename

but this means that you revert your entire index file to the old HEAD 
information, so you'll need to do git-update-cache on the files that you 
changed.

So:

> Or do I need todo a read-tree into a temporary index
> file. Check out the one file from this alternate index file and use
> update-cache to update my original index file?

Yes. If you want to touch just that one file, and you actually _want_ to
save all the other index information updates except for this one file. If
so, you can do

	# read a new index file with the HEAD information
	GIT_INDEX_FILE=tmp-index git-read-tree HEAD

	# check out just the one file you want to have
	GIT_INDEX_FILE=tmp-index git-checkout-cache -f filename

	# remove the now useless temporary index
	rm tmp-index

	# update your _real_ index file with the file information
	git-update-cache filename

and you're done - you've now updated only that _one_ file in your working 
area, and you've re-set the index file for that entry.

And yes, scripting it so that you don't make stupid mistakes is probably a
good idea. For exmple, if you misspell GIT_INDEX_FILE (like I did when I
write that at first), you'd have reverted your real index file after all.

In other words, the git core certainly is very flexible and can easily do 
what you want, but it's also certainly very very easy to screw up with.

		Linus

Re: Howto update a 'dirty' entry in the cache from the object database

[Junio C Hamano]

>>>>> "LT" == Linus Torvalds <torvalds@osdl.org> writes:

LT> On Wed, 4 May 2005, Thomas Glanzmann wrote:
>> 
>> I edited a bunch of files and notice that I want to revert back one of
>> the files to the original one (the one that comes with HEAD). But I
>> already updated the cache. Is there a way to 'patch' the cache with the
>> original file.

LT> Absolutely.

LT> You can do it several ways. The easiest one is

LT> 	git-read-tree -m HEAD
LT> 	git-checkout-cache -f filename

LT> but this means that you revert your entire index file to the old HEAD 
LT> information, so you'll need to do git-update-cache on the files that you 
LT> changed.

I think the easiest one that does not lose the cache for other
files is:

    git-diff-cache -z HEAD |
    GIT_EXTERNAL_DIFF=git-apply-patch-script \
        git-diff-tree-helper -z -R filename

This means: find diff from HEAD to the cache, and apply the diff
in the reverse, only to the filename.

Re: Howto update a 'dirty' entry in the cache from the object database

[Thomas Glanzmann]

Hello,

> 	# read a new index file with the HEAD information
> 	GIT_INDEX_FILE=tmp-index git-read-tree HEAD

> 	# check out just the one file you want to have
> 	GIT_INDEX_FILE=tmp-index git-checkout-cache -f filename

> 	# remove the now useless temporary index
> 	rm tmp-index

> 	# update your _real_ index file with the file information
> 	git-update-cache filename

thanks. That is exactly what I was looking for.

	Thomas