Git submodule repository locatio

Currently each submodule contains single .git file (instead of directory) with only link to project's base repository, for example "gitdir: ../../.git/modules/lib/neobundle.vim".

In git base repository we find .git/modules directory that contains bare repositories of all submodules, for example .git/modules/lib/neobundle.vim contains bare repository of neobundle submodule.

My proposal is to move default bare repository location from .git/modules to .git directory inside submodule, like every normal git repo do.

These are my arguments:

1. Why git submodule needs to know in which project it is embedded in? Or
even that it's generally submodule? When cd to submodule, it behaves like
normal repository. Only repository needs to know about its submodules.
2. You can't move submodule outside git repository and use it as normal git
repo. You have to copy bare repo from .git/modules dir.
3. It's not enough to delete submodule from workingdir to "refresh" it
later. You have to go to .git/modules directory and delete appropriate
folder.

What about performance on checkouts?

In systems supporting symlinks, the .git directory in submodule can be a symlink to the .git/modules subdirectory. In systems that do not support them, you can use mv-like command, that is very fast. Just move .git directory of submodule to .git/modules subdirectory, until you you need it (when you check out commit with "Subproject commit 55d868e(...) object").

I propose introducing this change in next major version of git, as it can break some scripts that depend on git submodule repository location.

Please consider this "feature request" seriously, most people I know think git submodules suck, and described issue is IMHO one of the reasons why.

Sincerely, Adam Stankiewicz (@sheerun)

On Wed, Apr 24, 2013 at 04:44:29PM +0200, Adam Stankiewicz wrote:

That's the way it was in old versions of git. The git-file approach was implemented so git could deal with adding or removing submodules. For example, if a submodule is not in version HEAD~ and you do a checkout HEAD~ your working dir should not contain the submodule. (Unfortunately we are not there quite yet).

A git submodule doesn't know about it's superproject. All git repos can be used with git-files. I wouldn't say that a .git-file makes a git repo aware that it's a subproject (which doesn't even had to be true).

The superproject needs to work with the working-tree, having repo data in the worktree like svn and cvs is a bad thing. I really like having all meta data in the same spot.

And there's the "checkout old commit without submodule" problem but of course, your "mv-approach" would solve this.

You can, if you edit .git-file. However in either case your can't use your superrepo in a sane way if you move out your submodule. So why would you do that?

If you only need the submodule repo, just clone the submodule repo.

I think that performance penalty is too small to be cared about, if you look at all the other file access stuff that git does every time.