Doing Bad and Feeling Bad
++libgit2
++libgit2
API updates.
++libgit2
++libgit2 for submodule ordering fix
++libgit2
++libgit2
Fix `userSignatureForNow` sometimes returning nil.

On the iOS simulator, `NSFullUserName()` (and presumably
`NSUserName()`) return an empty string; currently we check for nil.
This leads to `userSignatureForNow` returning nil and, eventually, a
crash. Instead make sure that `NSFullUserName()` and `NSUserName()`
don’t return an empty string or nil.
Use a simpler check.
It's == not !=.
Repeated calls are wasteful.
Also protect against an empty string user name.
Use stringWithFileSystemRepresentation: instead of...

stringWithUTF8String:
Header doc clean up.
Assert that file.path != NULL
Assertions go at the top.
Return nil if we can't create a file system path.
Merge pull request #353 from libgit2/gtdifffile-improvements

-stringWithFileSystemRepresentation instead of -stringWithUTF8String in GTDiffFile
++libgit2