Add ability to go back after following links

Mapped `<BS>` to go back to previous document after following a link,
works like a stack for following deeply nested links and coming back up
to the parents with each `<BS>`.

Author: dhruvasagar

README.md

@@ -1,4 +1,4 @@
-# VIM Do Too v0.13.2 [![CircleCI](https://circleci.com/gh/dhruvasagar/vim-dotoo.svg?style=svg)](https://circleci.com/gh/dhruvasagar/vim-dotoo)
+# VIM Do Too v0.13.3 [![CircleCI](https://circleci.com/gh/dhruvasagar/vim-dotoo.svg?style=svg)](https://circleci.com/gh/dhruvasagar/vim-dotoo)
 An awesome task manager & clocker inspired by org-mode written in pure viml.
 
 ## Pre-requisites
@@ -24,6 +24,7 @@ accurate agenda information and also for faster updates to these files.
    * <kbd>\<C-C\>\<C-C\></kbd>: Normalize a date (fixes day name if incorrect)
    * <kbd>\<Tab></kbd>:  Cycle headline visibility similar to Org mode
    * <kbd>\<CR></kbd>:  Follow link under cursor
+   * <kbd>\<BS></kbd>:  Go back to previous document after following a link
 
    The <kbd>\<C-X\></kbd>, <kbd>\<C-A\></kbd>, and  <kbd>cic</kbd> commands all work with <kbd>.</kbd>
    if you have [repeat.vim](http://github.com/tpope/vim-repeat) installed

autoload/dotoo/link.vim

@@ -12,10 +12,29 @@ function! s:parse_links()
   return result
 endfunction
 
+let s:link_stack = []
+function! s:add_to_link_stack(bufnr)
+  let winid = winnr()
+  let item = {'bufnr': a:bufnr, 'from': extend([bufnr()], getcurpos())}
+  call add(s:link_stack, item)
+endfunction
+
+function! s:pop_from_link_stack()
+  if empty(s:link_stack) | return | endif
+
+  let last_entry = remove(s:link_stack, -1)
+  let bfnr = last_entry.from[0]
+  if bufnr() != bfnr
+    exec 'buffer' bfnr
+  endif
+  call setpos('.', last_entry.from[1:])
+endfunction
+
 function! s:goto_headline(headline)
   if empty(a:headline)
     return 0
   endif
+  call s:add_to_link_stack(bufnr(a:headline.file))
   call dotoo#agenda#goto_headline('edit', a:headline)
   return 1
 endfunction
@@ -60,9 +79,11 @@ function! s:goto_file(link)
 
   if filereadable(file)
     let found = 1
+    call bufload(file) " ensure buffer is loaded
   endif
 
   if found ==# 1
+    call s:add_to_link_stack(bufnr(file))
     exe 'edit' file
     return 1
   endif
@@ -111,3 +132,11 @@ function! dotoo#link#follow(cmd) abort
     endif
   endfor
 endfunction
+
+function! dotoo#link#stack() abort
+  return string(s:link_stack)
+endfunction
+
+function! dotoo#link#back() abort
+  call s:pop_from_link_stack()
+endfunction

doc/dotoo.txt

@@ -2,7 +2,7 @@
 -------------------------------------------------------------------------------
 
        DoToo, the awesome TODO management system inspired by Org-Mode.
-                                 Version 0.13.2
+                                 Version 0.13.3
 
                 Author: Dhruva Sagar (http://dhruvasagar.com)
               License: MIT (http://opensource.org/licenses/MIT)
@@ -44,6 +44,7 @@ GETTING STARTED                                           *dotoo-getting-started
               `<C-C><C-C>`: Normalize a date (fixes day name if incorrect)
               `<Tab>`:      Cycle headline visibility similar to Org mode
               `<CR>`:       Follow link under cursor
+              `<BS>`:       Go back to previous document after following a link
 
               They `<C-X>`, `<C-A>` and `cic` commands are repeatable using |.|
 

ftplugin/dotoo.vim

@@ -91,6 +91,9 @@ if !g:dotoo_disable_mappings
   if !hasmapto('<Plug>(dotoo-link-follow)')
     nmap <buffer> <CR> <Plug>(dotoo-link-follow)
   endif
+  if !hasmapto('<Plug>(dotoo-link-back)')
+    nmap <buffer> <BS> <Plug>(dotoo-link-back)
+  endif
   if !hasmapto('<Plug>(dotoo-date-normalize)')
     nmap <buffer> <C-C><C-C> <Plug>(dotoo-date-normalize)
   endif

plugin/dotoo.vim

@@ -50,6 +50,9 @@ nnoremap <silent> <Plug>(dotoo-capture)
 nnoremap <silent> <Plug>(dotoo-link-follow)
       \ :<C-U>call dotoo#link#follow('edit')<CR>
 
+nnoremap <silent> <Plug>(dotoo-link-back)
+      \ :<C-U>call dotoo#link#back()<CR>
+
 nnoremap <silent> <Plug>(dotoo-date-increment)
       \ :<C-U>call dotoo#date#increment(v:count1)<CR>
 nnoremap <silent> <Plug>(dotoo-date-decrement)