[PATCH] dev-manual: correct inaccurate explanation of buildhistory setup

At the moment, the introduction to the buildhistory class suggests
that the developer needs to add the line:

  BUILDHISTORY_COMMIT = "1"

to their config file. Obviously, this is untrue since it is already
set to that by default in the buildhistory.bbclass file so remove that
directive but clarify that there is a reason why they might want to
subsequently set it zero.

Signed-off-by: Robert P. J. Day <[email protected]>

---

diff --git a/documentation/dev-manual/build-quality.rst b/documentation/dev-manual/build-quality.rst
index c3c7ccbb2..3c1dca2a2 100644
--- a/documentation/dev-manual/build-quality.rst
+++ b/documentation/dev-manual/build-quality.rst
@@ -33,13 +33,10 @@ The remainder of this section describes the following:
 Enabling and Disabling Build History
 ====================================

-Build history is disabled by default. To enable it, add the following
-:term:`INHERIT` statement and set the :term:`BUILDHISTORY_COMMIT` variable to
-"1" at the end of your ``conf/local.conf`` file found in the
-:term:`Build Directory`::
+Build history is disabled by default. To enable it, simply add the following
+:term:`INHERIT` statement at the end of your ``conf/local.conf`` file::

    INHERIT += "buildhistory"
-   BUILDHISTORY_COMMIT = "1"

 Enabling build history as
 previously described causes the OpenEmbedded build system to collect
@@ -52,9 +49,27 @@ build output information and commit it as a single commit to a local
    particularly for images, and increases the amount of disk space used
    during the build.

-You can disable build history by removing the previous statements from
+You can disable build history by removing that INHERIT statement from
 your ``conf/local.conf`` file.

+.. note::
+
+   To enable basic build history, you need only add the line::
+
+      INHERIT += "buildhistory"
+
+   to your local configuration, but the subsequent generation of that history
+   is actually controlled by the :term:`BUILDHISTORY_COMMIT` variable
+   which is, by default, already conditionally set to "1" in the
+   ``buildhistory.bbclass`` file::
+
+      BUILDHISTORY_COMMIT ?= "1"
+
+   so there is no need for you to set that variable yourself. However, as
+   you will see later in this section, you can inherit that class file
+   yet set that variable to zero if you don't want the history but
+   still want some of the other information produced by this feature.
+
 Understanding What the Build History Contains
 =============================================