Implement lfs.realpath()

[n1tehawk]

The function wraps realpath() for POSIX systems, and uses _fullpath() to achieve something similar on Windows. For now, I've deliberately chosen not to hide different / OS-specific behavior caused by the underlying implementation - e.g. Windows will not complain on non-existent paths.

This pull request addresses #64.

Regards, NiteHawk

[coveralls]

Coverage increased (+0.7%) to 78.788% when pulling 84628e4 on n1tehawk:20161018_realpath into 3c4e563 on keplerproject:master.

[hishamhm]

This is a welcome addition! :)

For now, I've deliberately chosen not to hide different / OS-specific behavior caused by the underlying implementation - e.g. Windows will not complain on non-existent paths.

I think lfs should strive to hide OS differences as much as possible. I remember we already have some headaches when other functions did not follow this principle, let's not add more portability corner cases.

Related question: does the Windows version resolve symlinks?

Also, this PR should target branch 1.7 since it adds to the API.

[coveralls]

Coverage increased (+0.7%) to 78.788% when pulling 2ad5d9a on n1tehawk:20161018_realpath into 3c4e563 on keplerproject:master.

[n1tehawk]

I think lfs should strive to hide OS differences as much as possible. I remember we already have some headaches when other functions did not follow this principle, let's not add more portability corner cases.

I understand that concern, but a cross-platform wrapper isn't trivial - especially as _fullpath doesn't seem to care about non-existing components in the path.

Related question: does the Windows version resolve symlinks?

Unfortunately: No. - according to my (preliminary) testing. :( This is likely again related to the fact that the Windows function doesn't care about the actual filesystem, but simply applies certain rules to "canonicalize" the given path; as illustrated by _fullpath("C:\\foo\\..\\bar") .

My impression is that support for the Windows platform - and especially handling "symlinks" (NTFS reparse points) - would benefit from some major refactoring and possibly introducing some platform-specific helper functions (which probably makes it a candidate for the 2.0 version). I'll have to further investigate that when I find some time.

Regards, NiteHawk