Bugfix: Shell variables shouldn't be overridden

Obviously this is something that, if we load ZSH and then load Bash, SHELL_HOME
is already going to be set to the ZSH home and therefore will not be reset to
the proper value of the Bash home.

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Signed-off-by: Jeff Felchner <accounts+git@thekompanee.com>
Bugfix: Fix backmerge not working properly

Now that we're referencing something from our git plugin, we need to source the
file first to get access to it.

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Signed-off-by: Jeff Felchner <accounts+git@thekompanee.com>