nvim: Remove mergetool and switch to DiffConflicts for git merge

Also add the conflict-marker plugin. This should also be useful
for doing rebases and resolving conflicts. Might drop one later
if one of them serves all the purposes in all cases.

While at it, add unimpaired style bindings for moving between
tabs. This is required since :DiffConflictsShowHistory opens
a new tab and default tab navigation bindings gt/gT at least
are binded to something else in python.

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>

git/.gitconfig

@@ -13,8 +13,9 @@
 [http]
 	sslVerify = false
 [merge]
-	tool = vim_mergetool
+	tool = diffconflicts
 	conflictstyle=diff3
-[mergetool "vim_mergetool"]
-	cmd = nvim -f -c "MergetoolStart" "$MERGED" "$BASE" "$LOCAL" "$REMOTE"
+[mergetool "diffconflicts"]
+	cmd = nvim -c "DiffConflicts" "$MERGED" "$BASE" "$LOCAL" "$REMOTE"
 	trustExitCode = true
+	keepBackup = false

nvim/.config/nvim/init.vim

@@ -31,7 +31,7 @@ Plug 'lervag/vimtex'
 Plug 'lambdalisue/gina.vim'
 Plug 'airblade/vim-gitgutter'
 Plug 'rhysd/git-messenger.vim'
-Plug 'samoshkin/vim-mergetool'
+Plug 'rhysd/conflict-marker.vim'
 Plug 'whiteinge/diffconflicts'
 " Boost vim command line mode
 Plug 'vim-utils/vim-husk'
@@ -236,6 +236,10 @@ nnoremap [b :bprevious<CR>
 nnoremap ]b :bnext<CR>
 nnoremap [B :bfirst<CR>
 nnoremap ]B :blast<CR>
+nnoremap [t :tabprevious<CR>
+nnoremap ]t :tabnext<CR>
+nnoremap [T :tabfirst<CR>
+nnoremap ]T :tablast<CR>
 nnoremap <Leader>b  :b<SPACE>
 nnoremap <Leader>bl :ls<CR>:b<SPACE>
 nnoremap <Leader>bd :bd<SPACE>
@@ -265,13 +269,6 @@ nnoremap <Leader>gB  :Gina branch<SPACE>
 nnoremap <Leader>go  :Gina checkout<SPACE>
 nnoremap <Leader>g-  :Gina stash<CR>:e<CR>
 nnoremap <Leader>g+  :Gina stash<SPACE>
-" Git merge tool
-nnoremap <Leader>ml :MergetoolDiffExchangeLeft<CR>
-nnoremap <Leader>mr :MergetoolDiffExchangeRight<CR>
-nnoremap <Leader>mu :MergetoolDiffExchangeUp<CR>
-nnoremap <Leader>md :MergetoolDiffExchangeDown<CR>
-nnoremap <Leader>mg :diffget<CR>
-nnoremap <Leader>mp :diffput<CR>
 " For gitgutter
 nnoremap ]h :GitGutterNextHunk<CR>
 nnoremap [h :GitGutterPrevHunk<CR>
@@ -483,10 +480,6 @@ let g:loaded_perl_provider = 0
 let g:loaded_node_provider = 0
 let g:python3_host_prog = '/usr/bin/python3'
 
-" Mergetool
-let g:mergetool_layout = 'mr'
-let g:mergetool_prefer_revision = 'unmodified'
-
 " Floaterm
 let g:floaterm_open_in_root  = 0
 let g:floaterm_position      = 'center'