Re: Git gc removes all packs

On 02/05/2015 09:03 PM, Jeff King wrote:

On Thu, Feb 05, 2015 at 04:13:03PM +0100, Dmitry Neverov wrote:

quoted

[...]
One more thing about my setup: since git p4 promotes a use of a linear
history I use a separate repository for another branch in perforce. In
order to be able to cherry-pick between repositories I added this
another repo objects dir as an alternate and also added a ref which is a
symbolic link to a branch in another repo (so I don't have to do any
fetches).

You can't symlink refs like this. The loose refs in the filesystem may
be migrated into the "packed-refs" file, at which point your symlink
will be broken. That is a likely reason why git would not find any refs.

So your setup will not ever work reliably.  But IMHO, it is a bug that
git does not notice the broken symlink and abort an operation which is
computing reachability in order to drop objects. As you noticed, it
means a misconfiguration or filesystem error results in data loss.

There's a bunch of code in refs.c that is there explicitly for reading
loose references that are symlinks. If the link contents literally start
with "refs/", then they are read and treated as a symbolic ref.
Otherwise, the symlink is just followed.

It is still possible to write symbolic refs that are represented as
symlinks (see core.preferSymlinkRefs), but that backwards-compatibility
code was added in 2006(!) Maybe it's time to deprecate it. And maybe we
should start working towards a future where any symlinks under "refs"
cause git to complain.

Michael

-- 
Michael Haggerty
mhagger@alum.mit.edu