MT#15803 Introducing the new function to provide current branch status

Previously we guessed the status of current branch by parsing
'git status' output. Unfortunately we have to care about a
corner cases in this way. In the same time we can easily
consider current branch status comparing commits.

Introducing the new function to provide current branch status:
up-2-date, ahead, behind or diverged with origin.

Change-Id: I4d09c8867069ccafc97e5d31638e8bc94caa58cd

functions/main

@@ -47,6 +47,34 @@ log_debug() {
     console_output "DEBUG: $*\n"
   fi
 }
+
+get_branch_status() {
+  log_debug "cd $NGCPCTL_MAIN"
+  cd "$NGCPCTL_MAIN"
+
+  log_debug "git rev-parse HEAD"
+  local LOCAL=$(git rev-parse HEAD)
+
+  log_debug "git rev-parse @{u}"
+  local REMOTE=$(git rev-parse @{u})
+
+  log_debug "git merge-base HEAD @{u}"
+  local BASE=$(git merge-base HEAD @{u})
+
+  if [ "$LOCAL" = "$REMOTE" ]; then
+    # Up-to-date
+    return 0
+  elif [ "$LOCAL" = "$BASE" ]; then
+    # Need to pull
+    return 1
+  elif [ "$REMOTE" = "$BASE" ]; then
+    # Need to push
+    return 2
+  else
+    # Diverged
+    return 3
+  fi
+}
 ## }}}
 
 ## important variables we depend on to operate successfully {{{