This is a bugfix for an very particular issue.
Here's what happens:
If we create() an FileLockEntry and then update() it, we are running
into a problem because update() calls _update() which changes the
precense status of a FileLockEntry.
Because update() is _consuming_, the FileLockEntry gets drop()ed
afterwards. This _again_ causes _update() to be called, but with a new
presence status, which is not true in this moment (as the FileLockEntry
is still borrowed, but we already marked it as present).
This patch is a short-term fix. The real problem is, that our Store
interface is consuming. If the Store interface would be non-consuming,
this issue wouldn't happen, as the drop() call would not happen.
I'm rather sure that this patch will not be reverted in the process of
rewriting the Store interface to be non-consuming. But we never know.
to actually test:
1. get -> Should return Ok(None)
2. create -> Should return Ok(())
3. get -> Should return Ok(Some(_))
4. delete -> Should return Ok(())
5. get -> Should return Ok(None)
We must return an error if the file is not found here.
This is because if we unwrap() here, we panic if the store action was
Store::retrieve() and there wasn't a file there. We then unwrap() on
None and panic because of this, causing all other tests to panic as
well because the Mutex gets corrupted.
The store handles FileNotFound errors on its own, so it is safe to
return the error here.
This patch fixes the `impl Iterator for GlobStoreIdIterator` which used
the glob() result to fetch the files from the FS, but glob() returns the
absolute pathes (to filesystem root).
We have to strip the `store_path` prefix and use the local part for
building the StoreId object.
Having a ::is_in_collection() is a nice thing, though it is _way_ better
if we just give the user of the `StoreId` object access to the local
part of the ID.
Using this new function, one can do all the actions one might need on
the Path for the actual entry without nasty copying or such.
`StoreId::is_in_collection()` can be replaced by
`StoreId::local().starts_with()` and everything is fine, as we do not
have to move a `PathBuf` object into the function anymore.
