new: [myc-update] allow to update with an other branch than master

bin/myc-update

@@ -10,19 +10,26 @@ include pretty
 start=$SECONDS
 
 if [ -z "$NO_UPDATE" -a -d "/opt/apps/myc-manage" ]; then
+    MYC_UPDATE_VERSION="${MYC_UPDATE_VERSION:-master}"
     Elt "Checking if myc-manage requires update..."
     cd /opt/apps/myc-manage
-    REMOTE_HEAD="$(git ls-remote origin refs/heads/master 2>/dev/null | cut -f 1)"
+    REMOTE_HEAD="$(git ls-remote origin "refs/heads/${MYC_UPDATE_VERSION}" 2>/dev/null | cut -f 1)"
+    if [ -z "$REMOTE_HEAD" ]; then
+        err "Can't find remote branch '$MYC_UPDATE_VERSION'."
+        echo "  - Either this branch is not available on 'origin' remote." >&2
+        echo "  - Either 'origin' remote is not correctly set." >&2
+        exit 1
+    fi
     HEAD="$(git rev-parse HEAD)"
     if [ "$REMOTE_HEAD" != "$HEAD" ]; then
         print_info "new version available"
         Wrap -d "Update myc-manage" <<EOF || exit 1
 if ! [ -d "/opt/apps/myc-manage" ]; then
     mkdir -p /opt/apps && cd /opt/apps
-    git clone https://git.myceliandre.fr/Myceliandre/myc-manage.git
+    git clone https://git.myceliandre.fr/Myceliandre/myc-manage.git -b "$MYC_UPDATE_VERSION"
 else
     cd /opt/apps/myc-manage &&
-    git checkout master &&
+    git checkout "$MYC_UPDATE_VERSION" &&
     git pull -r || exit 1
 fi