Re: [PATCH] Add platform-independent .git "symlink"

["Shawn O. Pearce" <spearce@spearce.org>]

Johannes Schindelin <Johannes.Schindelin@gmx.de> wrote:
> Howver, having .git a file pointing to another git directory allows you to 
> have locks there.  And they can be actually pretty sensible locks, like
> 
> 	.git/HEAD.<mangled-path>
> 
> actually containing the symbolic ref describing which branch we're on in 
> that working directory.  Likewise, .git/index.<mangled-path> needs to hold 
> the current index.
> 
> Of course, for this to work, you need to use different HEADs and indexes 
> only if .git was a file originally.
> 
> BTW <mangled-path> could be a hash of the path, and for convenience, we 
> could store the path in .git/workdir.<mangled-path>.

This I like.  Because my day-job coworkers and I make very heavy use of
git-new-workdir to manage our compile areas/working directories.  :)

The biggest problem with new-workdir is the master repository
cannot see the HEAD, index or logs/HEAD of the working directories.
Consequently it is possible for prune (or repack -a -d) to remove
objects that some workdir is still referring to.  Its not uncommon
for my HEAD reflogs to have stale commits in them.  Every once in
a while a user looses their HEAD entirely when it gets pruned away,
as they had a workdir checked out on a detached HEAD.

The second biggest problem is checking out the same branch in two
different directories at once.  This becomes a problem only if you
modify the branch, but still, its a problem.


I was thinking that we could add a WORKDIR_HASH to the .git file
Lars was proposing.  This hash would be the <mangled-path> suffix
you are talking about above, and would avoid the need to compute
the absolute path for the working directory every time we run a
Git command.

The hash could be something simple, like the SHA-1 hash of the
absolute path at the time of workdir creation.  But it would be nice
if we could recommend a specific value during workdir creation,
so that the WORKDIR_HASH could start with a value that matches
something the user would readily recognize.

-- 
Shawn.