Question: .idx without .pack causes performance issues?

Hi all,

I just wanted to relay an issue we've seen before at my day job (and
it just recently cropped up again).  When moving users from Git for
Windows 1.8.3 to 1.9.5, we found a few users started having operations
take an excruciatingly long amount of time.  At some point, we traced
the issue to a number of .pack files had been deleted (possibly
garbage collected?) -- but their associated .idx files were still
present.  Upon removing the "orphaned" idx files, we found performance
returned to normal.  Otherwise, git fsck reported no issues with the
repositories.

Other users have noted that using git gc would sometimes correct the
issue for them, but not always.

Anyway, has anyone else experienced this performance degradation? I
have some feeling that it's an issue that may be exclusive to Windows
(or at least, only slow enough to matter on Windows), but I have no
proof, and I've never heard of an issue like this outside work. (One
idea that came to mind was even the .idx files were locked, and thus
not deleted.)  Something tells me deleting the orphaned .idx files
isn't the "nicest" solution, either.

Thanks!

--Doug

P.S. In addition to running the Git for Windows/msysgit builds, we
have a handful of users running Git Extensions as well, and also have
been seeing an increase in use of Visual Studio 2013 -- which of
course has libgit2 integrated. So, I think the chance that any one of
these might be using the repo or holding files open is very high.