add git helper and alias for updating another branch

git/gitconfig

@@ -30,6 +30,7 @@
     l = "!source ~/.githelpers && pretty_git_log"
     la = !git l --all
     sync = "!source ~/.githelpers && sync_to_remote"
+    bsync = "!source ~/.githelpers && update_branch"
 
     todo = grep --heading --break --ignore-case -e ' FIX: *' -e ' TODO: *'
     pr = "!source ~/.githelpers && get_pr"

git/githelpers

@@ -19,6 +19,7 @@ AUTHOR="%C(bold blue)<%an>%Creset"
 REFS="%C(red)%d%Creset"
 SUBJECT="%s"
 DEFAULT_REMOTE="upstream"
+ROOT_BRANCH="master"
 
 FORMAT="$HASH}$RELATIVE_TIME}$AUTHOR}$REFS $SUBJECT"
 
@@ -49,6 +50,22 @@ sync_to_remote() {
     git fetch ${REMOTE} && git rebase ${REMOTE}/${BRANCH};
 }
 
+update_branch() {
+    BRANCH=$1
+    : ${BRANCH:=$ROOT_BRANCH}
+    REMOTE=$2
+    : ${REMOTE:=$DEFAULT_REMOTE}
+    echo Updating ${BRANCH} from ${REMOTE}
+    # check stash stack before and after
+    old_stash=$(git rev-parse -q --verify refs/stash)
+    git stash
+    new_stash=$(git rev-parse -q --verify refs/stash)
+    # checkout branch and sync to remote, then come back
+    git checkout ${BRANCH} && git sync ${REMOTE} && git checkout -
+    # if the stash added to the stack, pop it back off
+    [ "$old_stash" != "$new_stash" ] && git stash pop
+}
+
 get_pr() {
     REMOTE=$2
     : ${REMOTE:="upstream"}