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, 17 insertions, 0 deletions

diff --git a/documentation/ref-manual/closer-look.xml b/documentation/ref-manual/closer-look.xml
index eccf97698a..c8f2fae94e 100644
--- a/documentation/ref-manual/closer-look.xml
+++ b/documentation/ref-manual/closer-look.xml
@@ -491,6 +491,14 @@
             <link linkend='var-DL_DIR'><filename>DL_DIR</filename></link>
             variable.
             This area is a cache that can hold previously downloaded source.
+            You can also instruct the OpenEmbedded build system to create
+            tarballs from Git repositories, which is not the default behavior,
+            and store them in the <filename>DL_DIR</filename> by using the
+            <link linkend='var-BB_GENERATE_MIRROR_TARBALLS'><filename>BB_GENERATE_MIRROR_TARBALLS</filename></link>
+            variable.
+        </para>
+
+        <para>
             Judicious use of a <filename>DL_DIR</filename> directory can
             save the build system a trip across the Internet when looking
             for files.
@@ -566,6 +574,15 @@
                 fetcher module.
             </para>
 
+            <note>
+                For information on how to have the OpenEmbedded build system
+                generate tarballs for Git repositories and place them in the
+                <link linkend='var-DL_DIR'><filename>DL_DIR</filename></link>
+                directory, see the
+                <link linkend='var-BB_GENERATE_MIRROR_TARBALLS'><filename>BB_GENERATE_MIRROR_TARBALLS</filename></link>
+                variable.
+            </note>
+
             <para>
                 When fetching a repository, BitBake uses the
                 <link linkend='var-SRCREV'><filename>SRCREV</filename></link>