[buildbot] phase1: manually fetch remote Git refs

[LEDE Commits]

jow pushed a commit to buildbot.git, branch master:
https://git.lede-project.org/eaf8408145a72e13fbb602c172487d644ab8cfc8

commit eaf8408145a72e13fbb602c172487d644ab8cfc8
Author: Jo-Philipp Wich <jo at mein.io>
AuthorDate: Wed Dec 14 18:28:58 2016 +0100

    phase1: manually fetch remote Git refs
    
    Buildbot never updates the remote branch reference on incremental updates,
    causing scripts/getver.sh to assume a dirty tree with unpublished local
    commits.
    
    Add a manual command step to update the remote branch ref in order to bring
    the remote tracking branch history in sync with the local branch.
    
    Signed-off-by: Jo-Philipp Wich <jo at mein.io>
---
 phase1/master.cfg | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/phase1/master.cfg b/phase1/master.cfg
index dc1e66d..b9bbf12 100644
--- a/phase1/master.cfg
+++ b/phase1/master.cfg
@@ -330,6 +330,14 @@ for target in targets:
 		mode = 'incremental',
 		method = 'clean'))
 
+	# update remote refs
+	factory.addStep(ShellCommand(
+		name = "fetchrefs",
+		description = "Fetching Git remote refs",
+		command = ["git", "fetch", "origin", "+refs/heads/%s:refs/remotes/origin/%s" %(repo_branch, repo_branch)],
+		haltOnFailure = True
+	))
+
 	# fetch tags
 	factory.addStep(ShellCommand(
 		name = "fetchtag",