[[!comment format=mdwn
 username="joey"
 subject="""comment 1"""
 date="2016-01-26T16:21:56Z"
 content="""
I can reproduce this with LANG=C.

The cause seems to be that concurrent-output uses Text internally, and
Strings encoded using the filesystem encoding fail to round-trip through
Text.

I tried changing concurrent-output from using `T.hPutStr stdout t` to
`hPutStr stdout (T.unpack t)` but that doesn't help; by the time the String
comes back out it's lost the filesystem encoding and so contains invalid
characters.

Seems that the only way to fix this would be to change concurrent-output
not to use Text. However, it can't use ByteString because it needs to
operate on individual unicode characters when updating a region.
Which leaves only String, which I fear would slow
concurrent-output down quite significantly.

(It might be possible to use ByteString for most of it, and fall back to
String only when calculating the display update and so avoid most of the
permformance impact. I have an incomplete conversion headed in that
direction in the use-bytestring branch in concurrent-output git repo. After
spending 2 hours on it, it's nowhere near done.)

Since git-annex remains usable without -J, and since this only affects
systems that don't have a unicode locale configured and yet are using
unicode filenames (or systems that do use a unicode locale and have
filenames that are not valid utf-8), I'm kind of inclined not to massively
rework and likely slow down concurrent-output just to handle this case.
But I don't like it.

Workaround: Compile git-annex with -f-ConcurrentOutput and the problem
will be avoided, although then you won't get progress displays when doing a
`git-annex get -Jn`
"""]]