feat: layout_strategies refactor (#1039)

* wip: 2021-07-22 15:00 BST

* wip: `horizontal` refactored

* wip: `center` refactored

* wip: `cursor` and `vertical` refactored

* wip: `current_buffer` refactor

- also changed `layout_config_defaults` as they gave errors when using `current_buffer`

* wip: `bottom_pane` refactor

* [docgen] Update doc/telescope.txt
skip-checks: true

* fix: put accidentally remove config option back

* [docgen] Update doc/telescope.txt
skip-checks: true

* wip: standardise `height` calculation for `center` and `bottom_pane`

* wip: improve comments

* [docgen] Update doc/telescope.txt
skip-checks: true

* stylua

- also fix a merge mistake

* [docgen] Update doc/telescope.txt
skip-checks: true

* fix: attempt to fix bad merge

* refactor: remove unused entry in `borderchars` table

- also fix some typos

* wip: tweak padding for `bottom_pane`

* wip: add `tabline` checks to `bottom_pane`

- also tweaked position so that `statusline` is not covered when borders are enabled

* stylua

* refactor: factor out size capping function

* [docgen] Update doc/telescope.txt
skip-checks: true

* fix: adjust tests that relied on height being number of results

* fix: forgot variable in calc_size_and_spacing

* fix: maybe this fixes these tests?

* test: try other plenary branch for ci

* test: switch back to main plenary branch for ci

* fix: actually define `max_results` in the test

* fix: final tweaks for edge cases

Co-authored-by: Github Actions <actions@github>

lua/telescope/themes.lua

@@ -47,7 +47,6 @@ function themes.get_dropdown(opts)
 
     border = true,
     borderchars = {
-      { "─", "│", "─", "│", "╭", "╮", "╯", "╰" },
       prompt = { "─", "│", " ", "│", "╭", "╮", "│", "│" },
       results = { "─", "│", "─", "│", "├", "┤", "╯", "╰" },
       preview = { "─", "│", "─", "│", "╭", "╮", "╯", "╰" },
@@ -85,7 +84,6 @@ function themes.get_cursor(opts)
       end,
     },
     borderchars = {
-      { "─", "│", "─", "│", "╭", "╮", "╯", "╰" },
       prompt = { "─", "│", " ", "│", "╭", "╮", "│", "│" },
       results = { "─", "│", "─", "│", "├", "┤", "╯", "╰" },
       preview = { "─", "│", "─", "│", "╭", "╮", "╯", "╰" },
@@ -120,10 +118,8 @@ function themes.get_ivy(opts)
 
     border = true,
     borderchars = {
-      "z",
       prompt = { "─", " ", " ", " ", "─", "─", " ", " " },
       results = { " " },
-      -- results = { "a", "b", "c", "d", "e", "f", "g", "h" },
       preview = { "─", "│", "─", "│", "╭", "╮", "╯", "╰" },
     },
   }, opts)