ref-manual: Document BUILDHISTORY_PATH_PREFIX_STRIP

(From yocto-docs rev: c834fab46794233864e6bcb587ab75f2bfa1631c)

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Reviewed-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/variables.rst

@@ -1021,6 +1021,20 @@ system and gives an overview of their function and contents.
 
          BUILDHISTORY_IMAGE_FILES ?= "/etc/passwd /etc/group"
 
+   :term:`BUILDHISTORY_PATH_PREFIX_STRIP`
+      When inheriting the :ref:`buildhistory <ref-classes-buildhistory>`
+      class, this variable specifies a common path prefix that should be
+      stripped off the beginning of paths in the task signature list when the
+      ``task`` feature is active in :term:`BUILDHISTORY_FEATURES`. This can be
+      useful when build history is populated from multiple sources that may not
+      all use the same top level directory.
+
+      By default, the ``buildhistory`` class sets the variable as follows::
+
+         BUILDHISTORY_PATH_PREFIX_STRIP ?= ""
+
+      In this case, no prefixes will be stripped.
+
    :term:`BUILDHISTORY_PUSH_REPO`
       When inheriting the :ref:`buildhistory <ref-classes-buildhistory>`
       class, this variable optionally specifies a remote repository to