[UPDATE][VIM] Use b:undo_ftplugin

You're supposed to undo the changes that you made to a buffer's
variables when doing filetype-related settings. The variable
'b:undo_ftplugin' contains the commands necessary to revert any changes
that you have made to accomodate this filetype.

I removed the mappings for left and right in a quickfix windows because
I don't use them, and the 'qf' plug-in already maps those (meaning I had
an error when I tried to unmap them after qf already did so).

vim/.vim/after/ftplugin/bash.vim

@@ -1,8 +1,11 @@
 " Use shfmt as ALE fixer for bash
 let b:ale_fixers=[ 'shfmt' ]
+let b:undo_ftplugin.='|unlet b:ale_fixers'
 
 " Indent with 4 spaces, simplify script, indent switch cases, use Bash variant
 let b:ale_sh_shfmt_options='-i 4 -s -ci -ln bash'
+let b:undo_ftplugin.='|unlet b:ale_sh_shfmt_options'
 
 " Use bash dialect explicitly, require explicit empty string test
 let b:ale_sh_shellcheck_options='-s bash -o avoid-nullary-conditions'
+let b:undo_ftplugin.='|unlet b:ale_sh_shellcheck_options'

vim/.vim/after/ftplugin/c.vim

@@ -1,2 +1,3 @@
 " Use compile_commands.json to look for additional flags
 let b:ale_c_parse_compile_commands=1
+let b:undo_ftplugin.='|unlet b:ale_c_parse_compile_commands'

vim/.vim/after/ftplugin/cpp.vim

@@ -1,2 +1,3 @@
 " Use compile_commands.json to look for additional flags
 let b:ale_c_parse_compile_commands=1
+let b:undo_ftplugin.='|unlet b:ale_c_parse_compile_commands'

vim/.vim/after/ftplugin/d.vim

@@ -1,2 +1,3 @@
 " Use my desired ALE fixer for D
 let b:ale_fixers=[ 'dfmt' ]
+let b:undo_ftplugin.='|unlet b:ale_fixers'

vim/.vim/after/ftplugin/gitcommit.vim

@@ -1,2 +1,3 @@
 " Enable spell checking on commit messages
 setlocal spell
+let b:undo_ftplugin.='|setlocal spell<'

vim/.vim/after/ftplugin/json.vim

@@ -1,2 +1,3 @@
 " Use my desired ALE fixer for JSON
 let b:ale_fixers=[ 'jq' ]
+let b:undo_ftplugin.='|unlet b:ale_fixers'

vim/.vim/after/ftplugin/pandoc.vim

@@ -1,2 +1,3 @@
 " Let ALE know that I want Markdown linters
 let b:ale_linter_aliases=[ 'markdown' ]
+let b:undo_ftplugin.='|unlet b:ale_linter_aliases'

vim/.vim/after/ftplugin/python.vim

@@ -1,10 +1,13 @@
 " Use my desired ALE fixers for python
 let b:ale_fixers=[ 'black', 'isort' ]
+let b:undo_ftplugin.='|unlet b:ale_fixers'
 " Use my desired ALE linters for python
 let b:ale_linters=[ 'flake8', 'mypy', 'pylint', 'pyls' ]
+let b:undo_ftplugin.='|unlet b:ale_linters'
 
 "let b:ale_python_pyls_executable='pyls'
 let b:ale_python_pyls_auto_pipenv=1
+let b:undo_ftplugin.='|unlet b:ale_python_pyls_auto_pipenv'
 
 " Disable pycodestyle checks from pyls because I'm already using flake8
 let b:ale_python_pyls_config={
@@ -16,6 +19,8 @@ let b:ale_python_pyls_config={
   \         },
   \     },
   \  }
+let b:undo_ftplugin.='|unlet b:ale_python_pyls_config'
 
 " Change max length of a line to 88 for this buffer to match black's settings
 setlocal colorcolumn=88
+let b:undo_ftplugin.='|setlocal colorcolumn<'

vim/.vim/after/ftplugin/qf.vim

@@ -1,7 +1,5 @@
 " Use h/l to go to the previous/next non-empty quickfix or location list
 nnoremap <silent> <buffer> h :call quickfixed#older()<CR>
+let b:undo_ftplugin.='|nunmap <buffer> h'
 nnoremap <silent> <buffer> l :call quickfixed#newer()<CR>
-
-" Use left/right to go to the previous/next non-empty quickfix or location list
-nnoremap <silent> <buffer> <Left> :call quickfixed#older()<CR>
-nnoremap <silent> <buffer> <Right> :call quickfixed#newer()<CR>
+let b:undo_ftplugin.='|nunmap <buffer> l'

vim/.vim/after/ftplugin/rust.vim

@@ -1,2 +1,3 @@
 " Use rustfmt as ALE fixer for rust
 let b:ale_fixers=[ 'rustfmt' ]
+let b:undo_ftplugin.='|unlet b:ale_fixers'

vim/.vim/after/ftplugin/sh.vim

@@ -1,8 +1,11 @@
 " Use shfmt as ALE fixer for sh
 let b:ale_fixers=[ 'shfmt' ]
+let b:undo_ftplugin.='|unlet b:ale_fixers'
 
 " Indent with 4 spaces, simplify the code, indent switch cases, use POSIX
 let b:ale_sh_shfmt_options='-i 4 -s -ci -ln posix'
+let b:undo_ftplugin.='|unlet b:ale_sh_shfmt_options'
 
 " Require explicit empty string test
 let b:ale_sh_shellcheck_options='-o avoid-nullary-conditions'
+let b:undo_ftplugin.='|unlet b:ale_sh_shellcheck_options'

vim/.vim/after/ftplugin/zsh.vim

@@ -1,8 +1,11 @@
 " Use shfmt as ALE fixer for zsh
 let b:ale_fixers=[ 'shfmt' ]
+let b:undo_ftplugin.='|unlet b:ale_fixers'
 
 " Indent with 4 spaces, simplify script, indent switch cases, use Bash variant
 let b:ale_sh_shfmt_options='-i 4 -s -ci -ln bash'
+let b:undo_ftplugin.='|unlet b:ale_sh_shfmt_options'
 
 " Use bash dialect explicitly, require explicit empty string test
 let b:ale_sh_shellcheck_options='-s bash -o avoid-nullary-conditions'
+let b:undo_ftplugin.='|unlet b:ale_sh_shellcheck_options'