Previous to this patch, having a config like the following would not
work properly:
- link:
~/a: ~/b
This was because the '~' was expanded on the left hand side (the link
target), but not the right hand side (the link source). It was necessary
to use a workaround like this:
- link:
~/a: $HOME/b
This was because variable expansion was being done, but user expansion
was not being done.
This commit adds support for using '~' in the link source.
