There is already a partial test for this (network/log.sh). It fails
nowadays (again) because of patch index creation. See also issue76,
issue250, and issue385. Even if it doesn't fail (e.g. if you pass
--no-patch-index), creating a _darcs directory in some random place is
not nice behaviour.

Should also check that only relative paths are given.

See also issue459.

The following patch sent by Ben Franksen <benjamin.franksen@helmholtz-berlin.de> updated issue issue2461 with
status=resolved;resolvedin=2.12.0 HEAD

* resolve issue2461: darcs log --repo=remoterepo creates and populates _darcs 
Ignore-this: ba3d063f6a655f36b8d08ebcca6fcc8d

The solution is to make a case distinction between remote and local usage.
If we are working in a remote location, check that file arguments are
relative paths and then do the log action inside a temporary directory.

The following patch sent by Ben Franksen <benjamin.franksen@helmholtz-berlin.de> updated issue issue2461 with
status=resolved;resolvedin=2.12.0 HEAD

* resolve issue2461, this time also when no file names are specified 
Ignore-this: 9b51994e0a3fdb28d99a8856caa60e6e

Also slightly improve the error message when invalid arguments (non-relative
paths) are given for remote repos.