BUG: IOobject interpretation of ./ in construct-from-fileName (closes #482)

- Resolve ambiguity by using the following rules:

  1) starts with '/'  =>  absolute file-system path
  2) starts with './' or '../'  =>  file-system path relative to CWD
  3) otherwise treat as relative to the case

STYLE: allow write access to headerClassName

src/OpenFOAM/db/IOobject/IOobject.C

@@ -108,28 +108,22 @@ static inline bool isOutsideOfCase(const std::string& file)
 
 // * * * * * * * * * * * * Static Member Functions * * * * * * * * * * * * * //
 
-// Return components following the IOobject requirements
-//
-// behaviour
-//    input               IOobject(instance, local, name)
-//    -----               ------
-//    "foo"               ("", "", "foo")
-//    "foo/bar"           ("foo", "", "bar")
-//    "foo/bar/"          ERROR - no name
-//    "foo/xxx/bar"       ("foo", "xxx", "bar")
-//    "foo/xxx/yyy/bar"   ("foo", "xxx/yyy", "bar")
-//    "/xxx/yyy/bar"      ("/xxx/yyy", "", "bar")
 bool Foam::IOobject::fileNameComponents
 (
-    const fileName& rawPath,
+    const fileName& path,
     fileName& instance,
     fileName& local,
     word& name
 )
 {
-    // Re-interpret the path as a file-system path.
-    fileName path(rawPath);
-    path.toAbsolute();
+    // Convert explicit relative file-system path to absolute file-system path.
+    if (path.startsWith("./") || path.startsWith("../"))
+    {
+        fileName absPath = cwd()/path;
+        absPath.clean();
+
+        return fileNameComponents(absPath, instance, local, name);
+    }
 
     instance.clear();
     local.clear();

src/OpenFOAM/db/IOobject/IOobject.H

@@ -174,15 +174,15 @@ protected:
     // Protected Member Functions
 
         //- Construct and return an IFstream for the object.
-        //  The results is nullptr if the stream construction failed
+        // \Return nullptr if the stream construction failed
         Istream* objectStream();
 
-        //- Construct and return an IFstream for the object given the
-        //  exact file. The results is nullptr if the stream construction failed
-        Istream* objectStream(const fileName&);
+        //- Return an IFstream for the object given the exact file.
+        // \Return nullptr if the stream construction failed
+        Istream* objectStream(const fileName& fName);
 
         //- Set the object state to bad
-        void setBad(const string&);
+        void setBad(const string& s);
 
 
 public:
@@ -200,6 +200,20 @@ public:
     // Static Member Functions
 
         //- Split path into instance, local, name components
+        //
+        // The splitting behaviour is as follows:
+        // \verbatim
+        //    input       | instance   | local | name
+        //    ----------- | ---------- | ----- | ----
+        //    a           |            |       | a
+        //    a/b         | a          |       | b
+        //    a/b/c/d     | a          | b/c   | d
+        //    /a/b/c      | /a/b       |       | c
+        //    ./a/b/c     | PWD/a/b    |       | c
+        //    ../a/b/c    | PWD/../a/b |       | c
+        //    a/b/        | ERROR      |       |
+        // \endverbatim
+        // where PWD is the Foam::cwd() current working directory
         static bool fileNameComponents
         (
             const fileName& path,
@@ -240,9 +254,11 @@ public:
         );
 
         //- Construct from path, registry, io options.
-        //  Uses fileNameComponents() to split path into components. The
-        //  path argument is regarded as a file system path, not a case-relative
-        //  path. Any './' gets expanded to the current working directory.
+        //  Uses fileNameComponents() to split path into components.
+        //  A path that starts with a '/' is regarded as a file system path.
+        //  Paths starting with either './' or '../' are relative to
+        //  current working directory (and replaced with absolute equivalents).
+        //  All other paths are considered to be relative to the case.
         IOobject
         (
             const fileName& path,
@@ -300,6 +316,9 @@ public:
         //- Return name of the class name read from header
         inline const word& headerClassName() const;
 
+        //- Return non-constant access to the class name read from header
+        inline word& headerClassName();
+
         //- Return the optional note
         inline const string& note() const;
 

src/OpenFOAM/db/IOobject/IOobjectI.H

@@ -55,6 +55,12 @@ inline const Foam::word& Foam::IOobject::headerClassName() const
 }
 
 
+inline Foam::word& Foam::IOobject::headerClassName()
+{
+    return headerClassName_;
+}
+
+
 inline const Foam::string& Foam::IOobject::note() const
 {
     return note_;