list: Add TRANSFORM sub-command

Issue: #17823

Help/command/list.rst

@@ -151,6 +151,79 @@ REMOVE_DUPLICATES
 
 Removes duplicated items in the list.
 
+TRANSFORM
+"""""""""
+
+::
+
+  list(TRANSFORM <list> <ACTION> [<SELECTOR>]
+                        [OUTPUT_VARIABLE <output variable>])
+
+Transforms the list by applying an action to all or, by specifying a
+``<SELECTOR>``, to the selected elements of the list, storing result in-place
+or in the specified output variable.
+
+.. note::
+
+   ``TRANSFORM`` sub-command does not change the number of elements of the
+   list. If a ``<SELECTOR>`` is specified, only some elements will be changed,
+   the other ones will remain same as before the transformation.
+
+``<ACTION>`` specify the action to apply to the elements of list.
+The actions have exactly the same semantics as sub-commands of
+:command:`string` command.
+
+The ``<ACTION>`` may be one of:
+
+``APPEND``, ``PREPEND``: Append, prepend specified value to each element of
+the list. ::
+
+  list(TRANSFORM <list> <APPEND|PREPEND> <value> ...)
+
+``TOUPPER``, ``TOLOWER``: Convert each element of the list to upper, lower
+characters. ::
+
+  list(TRANSFORM <list> <TOLOWER|TOUPPER> ...)
+
+``STRIP``: Remove leading and trailing spaces from each element of the
+list. ::
+
+  list(TRANSFORM <list> STRIP ...)
+
+``GENEX_STRIP``: Strip any
+:manual:`generator expressions <cmake-generator-expressions(7)>` from each
+element of the list. ::
+
+  list(TRANSFORM <list> GENEX_STRIP ...)
+
+``REPLACE``: Match the regular expression as many times as possible and
+substitute the replacement expression for the match for each element
+of the list
+(Same semantic as ``REGEX REPLACE`` from :command:`string` command). ::
+
+  list(TRANSFORM <list> REPLACE <regular_expression>
+                                <replace_expression> ...)
+
+``<SELECTOR>`` select which elements of the list will be transformed. Only one
+type of selector can be specified at a time.
+
+The ``<SELECTOR>`` may be one of:
+
+``AT``: Specify a list of indexes. ::
+
+  list(TRANSFORM <list> <ACTION> AT <index> [<index> ...] ...)
+
+``FOR``: Specify a range with, optionaly, an incerment used to iterate over
+the range. ::
+
+  list(TRANSFORM <list> <ACTION> FOR <start> <stop> [<step>] ...)
+
+``REGEX``: Specify a regular expression. Only elements matching the regular
+expression will be transformed. ::
+
+  list(TRANSFORM <list> <ACTION> REGEX <regular_expression> ...)
+
+
 Sorting
 ^^^^^^^