largefiles: avoid use of uinitialized variable in case of errors

tests: remove unstable debugstate output in test-largefiles.t

largefiles: simplify lfutil.writehash This was unnecessarily verbose: there is no need to unlink the file when we open it for write anyway, and there is no need to check if the file exists after we created it.

merge with stable

largefiles: copy files into .hg/largefiles atomically Copying from the user cache into .hg/largefiles could fail halfway though with a partially written file.

largefiles: write .hg/largefiles/ files atomically Before, it was possible to create a .hg/largefiles/hash file with truncated content, i.e., content where SHA-1(content) != hash This breaks the fundamental invariant in largefiles that the file content for files in .hg/largefiles hash to the filename.

largefiles: add comment about non-atomic working directory When updating the working copy with a normal 'hg update', we also don't use atomic writes.

tests: use an alias to make msys 'pwd' return paths with forward slashes

tests: skip cvs tests with msys on windows They will fail with weird 'ssh' errors.

tests: introduce 'hghave msys' to skip tests that would fail because of msys

merge with stable

convert: handle trailing slashes in filemap better (issue3124)