Make `-[NSError git_errorFor:withAdditionalDescription:]` a vararg method.
Merge branch 'rename-sha-oid' into HEAD
Incorrect return type.
Use the new vararg method to give additional information in error messages.
Same line-ing.
Build a more Cocoa-like error

with the libgit2 error set as underlying the newly-created one.
Merge branch 'master' into vararg-error
Use the vararg.
Protect against nil libgit2 errors.
Style.
Merge pull request #218 from tiennou/vararg-error

Make `-[NSError git_errorFor:withAdditionalDescription:]` a vararg method.