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/config.lua

@@ -76,25 +76,35 @@ function config.set_pickers(pickers)
 end
 
 local layout_config_defaults = {
-  width = 0.8,
-  height = 0.9,
 
   horizontal = {
+    width = 0.8,
+    height = 0.9,
     prompt_position = "bottom",
     preview_cutoff = 120,
   },
 
   vertical = {
+    width = 0.8,
+    height = 0.9,
     preview_cutoff = 40,
   },
 
   center = {
+    width = 0.8,
+    height = 0.9,
     preview_cutoff = 40,
   },
 
   cursor = {
+    width = 0.8,
+    height = 0.9,
     preview_cutoff = 40,
   },
+
+  bottom_pane = {
+    height = 25,
+  },
 }
 
 local layout_config_description = string.format(