get_filename_component: Teach new BASE_DIR parameter.

In the get_filename_component command, add a new BASE_DIR parameter to
use with the ABSOLUTE and REALPATH options.  This will be used when
finding an absolute path from a relative path.

1 files changed, 32 insertions, 5 deletions

diff --git a/Help/command/get_filename_component.rst b/Help/command/get_filename_component.rst
index 60488da..82f9120 100644
--- a/Help/command/get_filename_component.rst
+++ b/Help/command/get_filename_component.rst
@@ -3,6 +3,8 @@ get_filename_component
 
 Get a specific component of a full filename.
 
+------------------------------------------------------------------------------
+
 ::
 
   get_filename_component(<VAR> <FileName> <COMP> [CACHE])
@@ -15,8 +17,6 @@ Set ``<VAR>`` to a component of ``<FileName>``, where ``<COMP>`` is one of:
  NAME      = File name without directory
  EXT       = File name longest extension (.b.c from d/a.b.c)
  NAME_WE   = File name without directory or longest extension
- ABSOLUTE  = Full path to file
- REALPATH  = Full path to existing file with symlinks resolved
  PATH      = Legacy alias for DIRECTORY (use for CMake <= 2.8.11)
 
 Paths are returned with forward slashes and have no trailing slahes.
@@ -24,14 +24,41 @@ The longest file extension is always considered.  If the optional
 ``CACHE`` argument is specified, the result variable is added to the
 cache.
 
+------------------------------------------------------------------------------
+
+::
+
+  get_filename_component(<VAR> <FileName>
+                         <COMP> [BASE_DIR <BASE_DIR>]
+                         [CACHE])
+
+Set ``<VAR>`` to the absolute path of ``<FileName>``, where ``<COMP>`` is one
+of:
+
+::
+
+ ABSOLUTE  = Full path to file
+ REALPATH  = Full path to existing file with symlinks resolved
+
+If the provided ``<FileName>`` is a relative path, it is evaluated relative
+to the given base directory ``<BASE_DIR>``.  If no base directory is
+provided, the default base directory will be
+:variable:`CMAKE_CURRENT_SOURCE_DIR`.
+
+Paths are returned with forward slashes and have no trailing slahes.  If the
+optional ``CACHE`` argument is specified, the result variable is added to the
+cache.
+
+------------------------------------------------------------------------------
+
 ::
 
-  get_filename_component(<VAR> FileName
+  get_filename_component(<VAR> <FileName>
                          PROGRAM [PROGRAM_ARGS <ARG_VAR>]
                          [CACHE])
 
-The program in ``FileName`` will be found in the system search path or
+The program in ``<FileName>`` will be found in the system search path or
 left as a full path.  If ``PROGRAM_ARGS`` is present with ``PROGRAM``, then
-any command-line arguments present in the ``FileName`` string are split
+any command-line arguments present in the ``<FileName>`` string are split
 from the program name and stored in ``<ARG_VAR>``.  This is used to
 separate a program name from its arguments in a command line string.