[DavSanchez]

The abbreviation files merge their contents into the user's config with a
record spread:

$env.config.abbreviations = {
    ...$git_abbreviations
    ...$env.config.abbreviations
}

That precedence (user config wins) is right, but the spread errors when a
key exists in both records instead of overriding it:

$env.config.abbreviations = { grbm: "git rebase main" }
source ./git-abbreviations.nu
# Error: nu::shell::column_defined_twice
#   x Record field or table column used twice: grbm

So a user cannot override an abbreviation before sourcing the file (which
is the documented way to keep config in config.nu), and sourcing the same
file twice fails too.

merge keeps the same precedence and doesn't care about duplicate keys:

$env.config.abbreviations = ($git_abbreviations | merge $env.config.abbreviations)

Verified on nushell 0.116.1 for all six abbreviation files: sourcing twice and
pre-defining a key both work, and the user's value still wins.

[fdncred]

good idea. ping me when you're ready

[DavSanchez]

@fdncred ready for review!

[fdncred]

Thanks