Help: Reorganise FILE_SETS and related properties

Reduce duplication and make the docs for target_sources() focus
on the functionality rather than the properties it modifies.
The properties are a lower level quantity, so put the relevant
details for them in the property documentation. The target_sources()
command only needs to reference the properties, not reproduce
the property documentation.

Improve the cross-referencing between the HEADER_... property
docs. This helps build the mental picture of how they relate to
each other.

6 files changed, 58 insertions, 22 deletions

diff --git a/Help/prop_tgt/HEADER_DIRS.rst b/Help/prop_tgt/HEADER_DIRS.rst
index 6cdd4f1..d095345 100644
--- a/Help/prop_tgt/HEADER_DIRS.rst
+++ b/Help/prop_tgt/HEADER_DIRS.rst
@@ -3,6 +3,12 @@ HEADER_DIRS
 
 .. versionadded:: 3.23
 
-Semicolon-separated list of base directories of the default header set created
-by :command:`target_sources(FILE_SET)`. This property supports
-:manual:`generator expressions <cmake-generator-expressions(7)>`.
+Semicolon-separated list of base directories of the target's default
+header set (i.e. the file set with name and type ``HEADERS``). The property
+supports :manual:`generator expressions <cmake-generator-expressions(7)>`.
+
+This property is normally only set by :command:`target_sources(FILE_SET)`
+rather than being manipulated directly.
+
+See :prop_tgt:`HEADER_DIRS_<NAME>` for the list of base directories in
+other header sets.
diff --git a/Help/prop_tgt/HEADER_DIRS_NAME.rst b/Help/prop_tgt/HEADER_DIRS_NAME.rst
index 7d282e5..dc73df7 100644
--- a/Help/prop_tgt/HEADER_DIRS_NAME.rst
+++ b/Help/prop_tgt/HEADER_DIRS_NAME.rst
@@ -3,6 +3,13 @@ HEADER_DIRS_<NAME>
 
 .. versionadded:: 3.23
 
-Semicolon-separated list of base directories of the header set with name
-``<NAME>`` created by :command:`target_sources(FILE_SET)`. This property
-supports :manual:`generator expressions <cmake-generator-expressions(7)>`.
+Semicolon-separated list of base directories of the target's ``<NAME>``
+header set, which has the set type ``HEADERS``. The property supports
+:manual:`generator expressions <cmake-generator-expressions(7)>`.
+
+This property is normally only set by :command:`target_sources(FILE_SET)`
+rather than being manipulated directly.
+
+See :prop_tgt:`HEADER_DIRS` for the list of base directories in the
+default header set. See :prop_tgt:`HEADER_SETS` for the file set names of all
+header sets.
diff --git a/Help/prop_tgt/HEADER_SET.rst b/Help/prop_tgt/HEADER_SET.rst
index eee834f..a703fc1 100644
--- a/Help/prop_tgt/HEADER_SET.rst
+++ b/Help/prop_tgt/HEADER_SET.rst
@@ -3,8 +3,13 @@ HEADER_SET
 
 .. versionadded:: 3.23
 
-Semicolon-separated list of headers in the default header set created by
-:command:`target_sources(FILE_SET)`. This property supports
-:manual:`generator expressions <cmake-generator-expressions(7)>`. If any of the
-headers are relative paths, they are computed relative to the target's source
-directory.
+Semicolon-separated list of files in the target's default header set,
+(i.e. the file set with name and type ``HEADERS``). If any of the paths
+are relative, they are computed relative to the target's source directory.
+The property supports
+:manual:`generator expressions <cmake-generator-expressions(7)>`.
+
+This property is normally only set by :command:`target_sources(FILE_SET)`
+rather than being manipulated directly.
+
+See :prop_tgt:`HEADER_SET_<NAME>` for the list of files in other header sets.
diff --git a/Help/prop_tgt/HEADER_SETS.rst b/Help/prop_tgt/HEADER_SETS.rst
index d07763b..fcf723e 100644
--- a/Help/prop_tgt/HEADER_SETS.rst
+++ b/Help/prop_tgt/HEADER_SETS.rst
@@ -3,6 +3,14 @@ HEADER_SETS
 
 .. versionadded:: 3.23
 
-List of ``PRIVATE`` and ``PUBLIC`` header sets added by
-:command:`target_sources(FILE_SET)`. Headers listed in these header sets are
-treated as source files for the purposes of IDE integration.
+List of the target's ``PRIVATE`` and ``PUBLIC`` header sets (i.e. all
+file sets with the type ``HEADERS``). Files listed in these file sets
+are treated as source files for the purpose of IDE integration.
+The files also have their :prop_sf:`HEADER_FILE_ONLY` property set to
+``TRUE``.
+
+This property is normally only set by :command:`target_sources(FILE_SET)`
+rather than being manipulated directly.
+
+See also :prop_tgt:`HEADER_SET_<NAME>`, :prop_tgt:`HEADER_SET` and
+:prop_tgt:`INTERFACE_HEADER_SETS`.
diff --git a/Help/prop_tgt/HEADER_SET_NAME.rst b/Help/prop_tgt/HEADER_SET_NAME.rst
index 3405690..e537f5a 100644
--- a/Help/prop_tgt/HEADER_SET_NAME.rst
+++ b/Help/prop_tgt/HEADER_SET_NAME.rst
@@ -3,8 +3,13 @@ HEADER_SET_<NAME>
 
 .. versionadded:: 3.23
 
-Semicolon-separated list of headers in the named header set ``<NAME>`` created
-by :command:`target_sources(FILE_SET)`. This property supports
-:manual:`generator expressions <cmake-generator-expressions(7)>`. If any of the
-headers are relative paths, they are computed relative to the target's source
-directory.
+Semicolon-separated list of files in the target's ``<NAME>`` header set,
+which has the set type ``HEADERS``. If any of the paths are relative,
+they are computed relative to the target's source directory. The property
+supports :manual:`generator expressions <cmake-generator-expressions(7)>`.
+
+This property is normally only set by :command:`target_sources(FILE_SET)`
+rather than being manipulated directly.
+
+See :prop_tgt:`HEADER_SET` for the list of files in the default header set.
+See :prop_tgt:`HEADER_SETS` for the file set names of all header sets.
diff --git a/Help/prop_tgt/INTERFACE_HEADER_SETS.rst b/Help/prop_tgt/INTERFACE_HEADER_SETS.rst
index 909510d..62db5b3 100644
--- a/Help/prop_tgt/INTERFACE_HEADER_SETS.rst
+++ b/Help/prop_tgt/INTERFACE_HEADER_SETS.rst
@@ -3,7 +3,12 @@ INTERFACE_HEADER_SETS
 
 .. versionadded:: 3.23
 
-List of ``INTERFACE`` and ``PUBLIC`` header sets added by
-:command:`target_sources(FILE_SET)`. Headers listed in these header sets can be
-installed with :command:`install(TARGETS)` and exported with
+List of the target's ``INTERFACE`` and ``PUBLIC`` header sets (i.e. all
+file sets with the type ``HEADERS``). Files listed in these header sets
+can be installed with :command:`install(TARGETS)` and exported with
 :command:`install(EXPORT)` and :command:`export`.
+
+This property is normally only set by :command:`target_sources(FILE_SET)`
+rather than being manipulated directly.
+
+See also :prop_tgt:`HEADER_SETS`.