fish: add external/bin from dotfiles to PATH

Signed-off-by: Christopher Larson <kergoth@gmail.com>
fish: fix value of SHELL variable

Signed-off-by: Christopher Larson <kergoth@gmail.com>
fish: alias dtrx

Signed-off-by: Christopher Larson <kergoth@gmail.com>
git-clone-via: don't choke if the source is a subdir of a repo

Signed-off-by: Christopher Larson <kergoth@gmail.com>