fetch2/git: Make git fetch run with -f so rebased branches don't fail

git fetches can fail (or at least return failed) when trying to
fetch and prune rebased branches. This patch simply adds a -f
to the git fetch command so these failure are ignore

Generally, if some SHA was rebased away it's not coming back so
there is no point in not doing this force

(Bitbake rev: a7b75e4db52445b30ec0fc0053dcf454f5f7d2db)

Signed-off-by: Matthew McClintock <msm@freescale.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/fetch2/git.py

@@ -190,7 +190,7 @@ class Git(FetchMethod):
                 logger.debug(1, "No Origin")
 
             runfetchcmd("%s remote add --mirror=fetch origin %s" % (ud.basecmd, repourl), d)
-            fetch_cmd = "%s fetch --prune %s refs/*:refs/*" % (ud.basecmd, repourl)
+            fetch_cmd = "%s fetch -f --prune %s refs/*:refs/*" % (ud.basecmd, repourl)
             bb.fetch2.check_network_access(d, fetch_cmd, ud.url)
             runfetchcmd(fetch_cmd, d)
             runfetchcmd("%s prune-packed" % ud.basecmd, d)