BugLink: http://bugs.launchpad.net/bugs/1693504

gen-auto-reconstruct script adds extend-diff-ignore options to
debian/source/options for symlinks not found in the orig tarball.

These options, however, are regular expressions, and match any part of a
file path. This may cause some files to be excluded from source when
they are not an exact match, but are a partial match to those symlinks.

Using beggining and end of string metacharacters fix the issue.

This problem was found in one of the derivatives, which contained a
symlink, whose name was a prefix for a directory in the same path,
leading that entire directory to be excluded from source.
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
[saf: escape literal '$' in string]
Acked-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>