'build' script: complain if we are not in a valid branch

This is a known problem and it is starting to become a FAQ.
People get an error message when they try to build a kernel
and they are not in a valid branch of their local repository.

When it happens git-branch will print something like:

* (no branch)
  andy-tracking
  balaji-tracking

With this patch we make sure we are in a valid branch when
building the kernel using the build script in order to avoid
OM developers some trouble. How? We print a nice message if
we are not in a valid branch and then stop.

Please feel free to edit the error message if you think it is
not clear enough.

Thanks to Werner Almesberger for his advice on shell scripting.

Signed-off-by: Nelson Castillo <arhuaco@freaks-unidos.net>

1 files changed, 12 insertions, 0 deletions

diff --git a/build b/build
index 58e24c7e624..34a34ed6a11 100755
--- a/build
+++ b/build
@@ -64,6 +64,18 @@ if [ -z "$PRODUCT" ] ; then
 fi
 
 #
+# check that we are in a valid branch
+#
+
+if git-branch | head -n1 | grep -q "* (no branch)"; then
+	cat <<EOF 1>&2
+There is no branch in the local copy of the repository right now!
+Hint: type git-branch, make sure you are in a valid branch and then try again
+EOF
+   exit 1
+fi;
+
+#
 # get the branch and head hash for the version we are building to
 # allow source tracability
 #