ref-manual, yocto-project-qs: Explanations for Git tarballs

Fixes [YOCTO #5035]

By default, the DL_DIR does not get files from Git repositories
that are suitable for mirroring.  There is a work-around by
using the BB_GENERATE_MIRROR_TARBALLS variable, which, when
set, causes the build system to generate tarballs for the
Git repositories and place them in the DL_DIR.

To address this, I added a new variable description for the
BB_GENERATE_MIRROR_TARBALLS varible, updated the DL_DIR
variable to indicate that "out-of-the-box" the YP puts suitable
mirror files into the DL_DIR for everthing except Git
repositories.

Some other sections were updated where discussion revolved around
pulling down source files.  The QS had a spot where the
BB_GENERATE_MIRROR_TARBALLS variable was actually used in an
example.  And, the expanded discussion on the BitBake process
had a couple spots that deserved a mention.

(From yocto-docs rev: 1539ff13222449ba60bfaaaac4fe1e8a795b0039)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/documentation/yocto-project-qs/yocto-project-qs.xml b/documentation/yocto-project-qs/yocto-project-qs.xml
index f212437f07..e33e4a6e4c 100644
--- a/documentation/yocto-project-qs/yocto-project-qs.xml
+++ b/documentation/yocto-project-qs/yocto-project-qs.xml
@@ -911,6 +911,17 @@
         </para>
 
         <para>
+            In the previous example, the
+            <ulink url='&YOCTO_DOCS_REF_URL;#var-BB_GENERATE_MIRROR_TARBALLS'><filename>BB_GENERATE_MIRROR_TARBALLS</filename></ulink>
+            variable causes the OpenEmbedded build system to generate tarballs
+            of the Git repositories and store them in the
+            <ulink url='&YOCTO_DOCS_REF_URL;#var-DL_DIR'><filename>DL_DIR</filename></ulink>
+            directory.
+            Due to performance reasons, generating and storing these tarballs
+            is not the build system's default behavior.
+        </para>
+
+        <para>
             You can also use the
             <ulink url='&YOCTO_DOCS_REF_URL;#var-PREMIRRORS'><filename>PREMIRRORS</filename></ulink>
             variable.