Commits on Jul 30, 2015

1. Simplify and fix os.MkdirAll() usage …

   TL;DR: check for IsExist(err) after a failed MkdirAll() is both
   redundant and wrong -- so two reasons to remove it.
   
   Quoting MkdirAll documentation:
   
   > MkdirAll creates a directory named path, along with any necessary
   > parents, and returns nil, or else returns an error. If path
   > is already a directory, MkdirAll does nothing and returns nil.
   
   This means two things:
   
   1. If a directory to be created already exists, no error is
   returned.
   
   2. If the error returned is IsExist (EEXIST), it means there exists
   a non-directory with the same name as MkdirAll need to use for
   directory. Example: we want to MkdirAll("a/b"), but file "a"
   (or "a/b") already exists, so MkdirAll fails.
   
   The above is a theory, based on quoted documentation and my UNIX
   knowledge.
   3. In practice, though, current MkdirAll implementation [1] returns
   ENOTDIR in most of cases described in moby#2, with the exception when
   there is a race between MkdirAll and someone else creating the
   last component of MkdirAll argument as a file. In this very case
   MkdirAll() will indeed return EEXIST.
   
   Because of moby#1, IsExist check after MkdirAll is not needed.
   
   Because of moby#2 and moby#3, ignoring IsExist error is just plain wrong,
   as directory we require is not created. It's cleaner to report
   the error now.
   
   [1] https://github.com/golang/go/blob/f9ed2f75/src/os/path.go
   
   Signed-off-by: Kir Kolyshkin <[email protected]>

   

   kolyshkin committed Jul 30, 2015
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