Fragile coding practices

The code like
```
	grep $short_refname "$GIT_DIR/locked"
	if [ $? -eq 0 ] ; then
```
is fragile - it is prone to break on future refactoring.
Also, it contains TWO other issues.

Much cleaner is to directly write what you intend the code to do:
```
	if grep -F "$short_refname" "$GIT_DIR/locked"; then
```