fix: The name is ....... sometimes too broad for a buffer

[abeldekat]

Fixes issue: #540

Related: This PR, regarding tests.

To consider:

1. Maybe there are more places where something similar happens
2. Maybe the question "is there a buffer with this exact name" should be asked to harpoon.buffer.lua
3. I could not get a test going. Perhaps, this is more an e2e test, needing a testdata folder, with 2 files and a harpoon.json

Non-failing test:

it("can handle the same filename in different directories", function()
    local file_one = "/tmp/namespace/init.lua"
    local buf_one = utils.create_file(file_one, { "foo", "bar" }, 1, 0)
    harpoon:list():append()

    local file_two = "/tmp/init.lua"
    local buf_two = utils.create_file(file_two, {
        "baz",
        "qux",
    }, 1, 0)
    harpoon:list():append()

    harpoon:sync()
    local list = harpoon:list()

    eq(list.items, {
        { value = file_one, context = { row = 1, col = 0 } },
        { value = file_two, context = { row = 1, col = 0 } },
    })

    vim.cmd("bwipeout! " .. buf_one)
    vim.cmd("bwipeout! " .. buf_two)

    harpoon:list():select(1)
    eq("/tmp/namespace/init.lua", vim.api.nvim_buf_get_name(0))
    harpoon:list():select(2)
    eq("/tmp/init.lua", vim.api.nvim_buf_get_name(0))
end)

[ThePrimeagen]

i can merge this, hodl

i hope this cures these weird file issues*