threads / rfc / 2639

[RFC] Make grafts versionable

Subject: [RFC] Make grafts versionable

## tl;dr

5 messages between Nov 21, 2005 and Nov 22, 2005.

replies: 4people: 3as markdown or json

Johannes Schindelin· Nov 21, 2005, 20:54 UTC · lore

... by moving the location from .git/info/grafts to .gitgrafts. This allows checking it in like .gitignore, and sure enough also pulling it (as well as knowing who the heck added that particular graft anyway).

Totally untested.
Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
---
	This would make half the discussion about rewriting history
	obsolete, methinks.
	Of course, to take advantage of it, you have to move the file 
	.git/info/grafts (if it exists) into the correct place yourself:
		mv -i .git/info/grafts .gitgrafts
 environment.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

applies-to: 20259f7c4418392e0e0c2f3a867811f657498afe a1756142e3be780ed7992cd6a3f5e64b53c42253

diff --git a/environment.c b/environment.c
index b5026f1..b0c2f79 100644
--- a/environment.c
+++ b/environment.c
@@ -35,7 +35,7 @@ static void setup_git_env(void)
 	}
 	git_graft_file = getenv(GRAFT_ENVIRONMENT);
 	if (!git_graft_file)
-		git_graft_file = strdup(git_path("info/grafts"));
+		git_graft_file = strdup(git_path("../.gitgrafts"));
 }
 
 char *get_git_dir(void)
---
0.99.9.GIT
H. Peter Anvin· Nov 21, 2005, 21:04 UTC · re: Johannes Schindelin · lore

Re: [RFC] Make grafts versionable

Johannes Schindelin wrote:
> ... by moving the location from .git/info/grafts to .gitgrafts. This 
> allows checking it in like .gitignore, and sure enough also pulling it (as 
> well as knowing who the heck added that particular graft anyway).

This is problematic, because it means something that isn't in GIT_DIR affects its interpretation. I would say that that is a showstopper.

One could even argue that it's incorrect, since it would mean different points on the history have different grafts.

Now, CVS has a reserved namespace (CVSROOT/) for things under version control which are still significant to CVS. The logical equivalent to git would be to have .git/ be such a namespace, if it makes sense.

	-hpa
Linus Torvalds· Nov 21, 2005, 21:35 UTC · re: H. Peter Anvin · lore

Re: [RFC] Make grafts versionable

On Mon, 21 Nov 2005, H. Peter Anvin wrote:
> 
> Now, CVS has a reserved namespace (CVSROOT/) for things under version control
> which are still significant to CVS.  The logical equivalent to git would be to
> have .git/ be such a namespace, if it makes sense.

Well, there's two reasons for disallowing git from tracking it's own .git directory:

 - it protects against people doing somethin glike
	git-update-cache --add -- $(find . -type f | cut -c3..)
   and finding the pre-existing files in ".git"
   This used to literally be how I imported trees into git. These days, 
   you can just do it with "git-ls-files --others", and in fact that is 
   exactly what "git add" does, so now you can just do
	git add .
   and be done with it - without getting that ".git" directory by mistake.
   So that _old_ reason may not be as valid any more.
However, there's one fundamental reason:
 - if you have a file in ".git", that implies that even a "raw git repo" 
   would have versions matter, since technically such a file would be 
   inside the "raw" part. And that I find to be confusing. One of the 
   whole points of a raw git repo is that because it doesn't have anything 
   that is version-controlled and checked out, none of the branches or 
   tags are special, and nothing needs to be updated when you push to such 
   a repo.
   Now, if you have files in .git, suddenly that fundamental nature of a 
   raw repository is no longer clear.

In general, making any internal git data versionable is very confusing. So you make the grafts file versionable - that suddenly means that different branches may have different parents for the same commit. And that depending on which branch you have checked out, git-fsck-cache may result in an error, or it may not. That's _nasty_, in my opinion.

So I much prefer to say: everything under ".git" is not versionable, for the fundamental reason that the files under .git are "global" to that git repository. 

And I think .git/grafts in particular makes no sense to version.

If you want to track a git "grafts" file, you can do it as another git repository and a symlink.

		Linus
H. Peter Anvin· Nov 21, 2005, 21:41 UTC · re: Linus Torvalds · lore

Re: [RFC] Make grafts versionable

Linus Torvalds wrote:
Show 14 quoted lines
> 
> However, there's one fundamental reason:
> 
>  - if you have a file in ".git", that implies that even a "raw git repo" 
>    would have versions matter, since technically such a file would be 
>    inside the "raw" part. And that I find to be confusing. One of the 
>    whole points of a raw git repo is that because it doesn't have anything 
>    that is version-controlled and checked out, none of the branches or 
>    tags are special, and nothing needs to be updated when you push to such 
>    a repo.
> 
>    Now, if you have files in .git, suddenly that fundamental nature of a 
>    raw repository is no longer clear.
>

Note that I didn't actually mean that they should necessarily represent files in .git/. The point was more that if we wanted to have version-controlled metadata, using .git/ as a namespace would be suitable.

In particular, I believe that if we ever do that, git should obtain this metadata from the repository/object database.

Show 14 quoted lines
> In general, making any internal git data versionable is very confusing. So 
> you make the grafts file versionable - that suddenly means that different 
> branches may have different parents for the same commit. And that 
> depending on which branch you have checked out, git-fsck-cache may result 
> in an error, or it may not. That's _nasty_, in my opinion.
> 
> So I much prefer to say: everything under ".git" is not versionable, for 
> the fundamental reason that the files under .git are "global" to that git 
> repository. 
> 
> And I think .git/grafts in particular makes no sense to version.
> 
> If you want to track a git "grafts" file, you can do it as another git 
> repository and a symlink.

I fully concur with this (as I pointed out in my post, although perhaps fuzzily.)

	-hpa
Johannes Schindelin· Nov 22, 2005, 00:37 UTC · re: Linus Torvalds · lore

Re: [RFC] Make grafts versionable

Hi,
On Mon, 21 Nov 2005, Linus Torvalds wrote:
Show 5 quoted lines
> In general, making any internal git data versionable is very confusing. So 
> you make the grafts file versionable - that suddenly means that different 
> branches may have different parents for the same commit. And that 
> depending on which branch you have checked out, git-fsck-cache may result 
> in an error, or it may not. That's _nasty_, in my opinion.

Yes, that is nasty. It does not reflect my normal usage pattern, but that does not make it better. So let's forget about that idea of mine.

Ciao, Dscho

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