1. git add file
2. git commit
3. modify file
4. git commit
5. git reset HEAD^
Before this fix, that resulted in git saying the file was modified. And
indeed, it didn't have the content it should in the just checked out ref,
because step 3 modified the object file for the old key.
When a v6 unlocked files is removed from the work tree,
unused doesn't show it. When it gets removed from the index,
unused does show it. This is the same as a locked file.
This only adds 1 stat to each file fscked for locked files, so
added overhead is minimal.
For unlocked files it has to access the database to see if a file
is modified.
If multiple files point to the same annex object, the user may want to
modify them independently, so don't use a hard link.
Also, check diskreserve when copying.
Note that the implementation uses replaceFile, so that the actual
replacement of the work tree file is atomic. This seems a good property to
have!
It would be possible for unlock in v6 mode to be run on files that do not
have their content present. However, that would be a behavior change from
before, and I don't see any immediate need to support it, so I didn't
implement it.
Before the smudge filter added a trailing newline, but other things that
wrote formatPointer to a file did not.
also some new pointer staging code to use later
This avoids querying the database when the content file doen't exist
(or otherwise fails the provided check). However, it does add overhead of
querying the database, and will certianly impact performance.
