On Thu, 16 Nov 2006, Johannes Sixt wrote: > > For one reason or another I would like to "clone" a local repo including the > checked-out working tree with cp -al instead of cg-clone/git-clone, i.e. > have all files hard-linked instead of copied. It works, but I don't think you should depend on it. > Can the copies be worked on independently without interference (with the git > tool set)? We _tried_ to make sure it is ok, but since it's not a normal mode of operation, I would not guarantee it. > One thing I noticed is that git-reset or probably git-checkout-index breaks > links of files that need not be changed by the reset. Yes and no. They do _not_ actually break links of files that they know stay the same, but your example breaks the internal knowledge by using that "cp -al". That changes the modification time of the inodes, so git thinks that the files _may_ have changed, and when you do a "git reset", it will overwrite them all. > Example: > > # make 2 files, commit > $ mkdir orig && cd orig > $ git-init-db > defaulting to local storage area > $ echo foo > a && cp a b && git-add a b && git-commit -a -m 1 > Committing initial tree 99b876dbe094cb7d3850f1abe12b4c5426bb63ea > > # 2nd commit modifies only one file: > $ echo bar > a && git-commit -a -m 2 > > # create the copy: > $ cd .. > $ cp -al orig copy > $ cd copy > > # working files are hard-linked: > $ ls -l > total 8 > -rw-r--r-- 2 jsixt users 4 Nov 16 19:24 a > -rw-r--r-- 2 jsixt users 4 Nov 16 19:23 b > > # nuke a commit: > $ git-reset --hard HEAD^ > $ ls -l > total 8 > -rw-r--r-- 1 jsixt users 4 Nov 16 19:24 a > -rw-r--r-- 1 jsixt users 4 Nov 16 19:24 b > > I'd have expected that the hard-link of b remained and only a's link were > broken. Does it mean that git-reset writes every single file also for large > trees like the kernel? I cannot believe this. Can someone scratch the > tomatoes off my eyes please? If you do a git update-index --refresh (or, more easily, a "git status", which will do the index refresh for you) before you do the "git reset", you will get: $ ls -l total 8 -rw-r--r-- 1 jsixt users 4 Nov 16 19:24 a -rw-r--r-- 2 jsixt users 4 Nov 16 19:24 b like you want to. The reason "git reset" overwrites _both_ files in your example is that the stat() information for those files changed, so "git reset" thinks they are both dirty and both need to be rewritten. That said, I would seriously suggest that you try these things out, and realize that most people do _not_ use the hardlinked approach. For all I know, some piece of git might change some files in-place. I don't _think_ we do, and it would strictly speaking be a bug, but because people don't use it that way, you'd be the guinea pig. I think we'll happily fix any bugs you find, but that may not make you any happier if the bug corrupted your lifes work ;) In general, you might want to use git clone -l -s instead, but that will _not_ hardlink the actual checked-out contents, so it's not going to get the kind of sharing you look for. On the other hand, especially with good maintenance (doing "git repack -l -d -a" etc), you may end up sharing _more_ that way at least in the repository object database (but never in the actual checked-out directories). Linus - To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html