defaults: enable 'autoindent' #2857

Re: https://github.com/neovim/neovim/issues/2676

runtime/doc/options.txt

@@ -718,7 +718,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 	further details see |arabic.txt|.
 
 			*'autoindent'* *'ai'* *'noautoindent'* *'noai'*
-'autoindent' 'ai'	boolean	(default off)
+'autoindent' 'ai'	boolean	(default on)
 			local to buffer
 	Copy indent from current line when starting a new line (typing <CR>
 	in Insert mode or when using the "o" or "O" command).  If you do not

runtime/doc/vim_diff.txt

@@ -29,6 +29,7 @@ these differences.
 2. Option defaults					  *nvim-option-defaults*
 
 - 'autoread' is set by default
+- 'autoindent' is set by default.
 - 'backspace' defaults to "indent,eol,start"
 - 'encoding' defaults to "utf-8"
 - 'formatoptions' defaults to "tcqj"

src/nvim/option.c

@@ -412,9 +412,9 @@ static vimoption_T
   {"autochdir",  "acd",   P_BOOL|P_VI_DEF,
    (char_u *)&p_acd, PV_NONE,
    {(char_u *)FALSE, (char_u *)0L} SCRIPTID_INIT},
-  {"autoindent",  "ai",   P_BOOL|P_VI_DEF,
+  {"autoindent",  "ai",   P_BOOL,
    (char_u *)&p_ai, PV_AI,
-   {(char_u *)FALSE, (char_u *)0L} SCRIPTID_INIT},
+   {(char_u *)FALSE, (char_u *)TRUE} SCRIPTID_INIT},
   {"autoread",    "ar",   P_BOOL|P_VIM,
    (char_u *)&p_ar, PV_AR,
    {(char_u *)FALSE, (char_u *)TRUE} SCRIPTID_INIT},

test/functional/helpers.lua

@@ -6,8 +6,9 @@ local AsyncSession = require('nvim.async_session')
 local Session = require('nvim.session')
 
 local nvim_prog = os.getenv('NVIM_PROG') or 'build/bin/nvim'
+--- FIXME: 'autoindent' messes up the insert() function
 local nvim_argv = {nvim_prog, '-u', 'NONE', '-i', 'NONE', '-N',
-                   '--cmd', 'set shortmess+=I background=light noswapfile',
+                   '--cmd', 'set shortmess+=I background=light noswapfile noautoindent',
                    '--embed'}
 
 -- Formulate a path to the directory containing nvim.  We use this to