patch 8.0.0716: not easy to start Vim cleanly

Problem:    Not easy to start Vim cleanly without changing the viminfo file.
            Not possible to know whether the -i command line flag was used.
Solution:   Add the --clean command line argument.  Add the 'viminfofile'
            option.  Add "-u DEFAULTS".

runtime/doc/debug.txt

@@ -1,4 +1,4 @@
-*debug.txt*     For Vim version 8.0.  Last change: 2012 Feb 11
+*debug.txt*     For Vim version 8.0.  Last change: 2017 Jul 15
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -53,7 +53,7 @@ Use this command to start Vim:
 	valgrind --log-file=valgrind.log --leak-check=full ./vim
 
 Note: Vim will run much slower.  If your .vimrc is big or you have several
-plugins you need to be patient for startup, or run with the "-u NONE"
+plugins you need to be patient for startup, or run with the "--clean"
 argument.
 
 There are often a few leaks from libraries, such as getpwuid() and

runtime/doc/options.txt

@@ -4966,8 +4966,8 @@ A jump table for the options with a short description can be found at |Q_op|.
 	When on the plugin scripts are loaded when starting up |load-plugins|.
 	This option can be reset in your |vimrc| file to disable the loading
 	of plugins.
-	Note that using the "-u NONE" and "--noplugin" command line arguments
-	reset this option. |-u| |--noplugin|
+	Note that using the "-u NONE", "-u DEFAULTS" and "--noplugin" command
+	line arguments reset this option.  See |-u| and |--noplugin|.
 
 						*'luadll'*
 'luadll'		string	(default depends on the build)
@@ -7330,7 +7330,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 
 	Watch out for errors in expressions.  They may render Vim unusable!
 	If you are stuck, hold down ':' or 'Q' to get a prompt, then quit and
-	edit your .vimrc or whatever with "vim -u NONE" to get it right.
+	edit your .vimrc or whatever with "vim --clean" to get it right.
 
 	Examples:
 	Emulate standard status line with 'ruler' set >
@@ -7755,7 +7755,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 	NOTE: This option is reset when 'compatible' is set.
 
 						*'termkey'* *'tk'*
-'termkey' 'tk'	string	(default "CTRL-W")
+'termkey' 'tk'		string	(default "CTRL-W")
 			local to window
 			{not in Vi}
 	The key that precedes a Vim command in a terminal window.  Other keys
@@ -8333,13 +8333,14 @@ A jump table for the options with a short description can be found at |Q_op|.
 			{not available when compiled without the |+viminfo|
 			feature}
 	When non-empty, the viminfo file is read upon startup and written
-	when exiting Vim (see |viminfo-file|).  The string should be a comma
-	separated list of parameters, each consisting of a single character
-	identifying the particular parameter, followed by a number or string
-	which specifies the value of that parameter.  If a particular
-	character is left out, then the default value is used for that
-	parameter.  The following is a list of the identifying characters and
-	the effect of their value.
+	when exiting Vim (see |viminfo-file|). Except when 'viminfofile' is
+	"NONE".
+	The string should be a comma separated list of parameters, each
+	consisting of a single character identifying the particular parameter,
+	followed by a number or string which specifies the value of that
+	parameter.  If a particular character is left out, then the default
+	value is used for that parameter.  The following is a list of the
+	identifying characters and the effect of their value.
 	CHAR	VALUE	~
 							*viminfo-!*
 	!	When included, save and restore global variables that start
@@ -8399,9 +8400,9 @@ A jump table for the options with a short description can be found at |Q_op|.
 		has been used since the last search command.
 							*viminfo-n*
 	n	Name of the viminfo file.  The name must immediately follow
-		the 'n'.  Must be at the end of the option!  If the "-i"
-		argument was given when starting Vim, that file name overrides
-		the one given here with 'viminfo'.  Environment variables are
+		the 'n'.  Must be at the end of the option!  If the
+		'viminfofile' option is set, that file name overrides the one
+		given here with 'viminfo'.  Environment variables are
 		expanded when opening the file, not when setting the option.
 							*viminfo-r*
 	r	Removable media.  The argument is a string (up to the next
@@ -8442,6 +8443,17 @@ A jump table for the options with a short description can be found at |Q_op|.
 	NOTE: This option is set to the Vim default value when 'compatible'
 	is reset.
 
+				*'viminfofile'* *'vif'*
+'viminfofile' 'vif'	string	(default: "")
+			global
+			{not in Vi}
+			{not available when compiled without the |+viminfo|
+			feature}
+	When non-empty, overrides the file name used for viminfo.
+	When equal to "NONE" no viminfo file will be read or written.
+	This option can be set with the |-i| command line flag.  The |--clean|
+	command line flag sets it to "NONE".
+
 					    *'virtualedit'* *'ve'*
 'virtualedit' 've'	string	(default "")
 			global

runtime/doc/starting.txt

@@ -1,4 +1,4 @@
-*starting.txt*  For Vim version 8.0.  Last change: 2017 Jan 15
+*starting.txt*  For Vim version 8.0.  Last change: 2017 Jul 15
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -140,11 +140,12 @@ a slash.  Thus "-R" means recovery and "-/R" readonly.
 --noplugin	Skip loading plugins.  Resets the 'loadplugins' option.
 		{not in Vi}
 		Note that the |-u| argument may also disable loading plugins:
-			argument	load vimrc files	load plugins ~
-			(nothing)		yes		    yes
-			-u NONE			no		    no
-			-u NORC			no		    yes
-			--noplugin		yes		    no
+			argument   load: vimrc files  plugins  defaults.vim ~
+			(nothing)	     yes	yes	  yes
+			-u NONE		     no		no	  no
+			-u DEFAULTS	     no		no	  yes
+			-u NORC		     no		yes	  no
+			--noplugin	     yes	no	  yes
 
 --startuptime {fname}					*--startuptime*
 		During startup write timing messages to the file {fname}.
@@ -465,21 +466,30 @@ a slash.  Thus "-R" means recovery and "-/R" readonly.
 --nofork	GUI: Do not fork.  Same as |-f|.
 							*-u* *E282*
 -u {vimrc}	The file {vimrc} is read for initializations.  Most other
-		initializations are skipped; see |initialization|.  This can
-		be used to start Vim in a special mode, with special
+		initializations are skipped; see |initialization|.
+
+		This can be used to start Vim in a special mode, with special
 		mappings and settings.  A shell alias can be used to make
 		this easy to use.  For example: >
 			alias vimc vim -u ~/.c_vimrc !*
 <		Also consider using autocommands; see |autocommand|.
+
 		When {vimrc} is equal to "NONE" (all uppercase), all
 		initializations from files and environment variables are
 		skipped, including reading the |gvimrc| file when the GUI
 		starts.  Loading plugins is also skipped.
+
 		When {vimrc} is equal to "NORC" (all uppercase), this has the
 		same effect as "NONE", but loading plugins is not skipped.
-		Using the "-u" argument has the side effect that the
-		'compatible' option will be on by default.  This can have
-		unexpected effects.  See |'compatible'|.
+
+		When {vimrc} is equal to "DEFAULTS" (all uppercase), this has
+		the same effect as "NONE", but the |defaults.vim| script is
+		loaded, which will also set 'nocompatible'.
+
+		Using the "-u" argument with another argument than DEFAULTS
+		has the side effect that the 'compatible' option will be on by
+		default.  This can have unexpected effects.  See
+		|'compatible'|.
 		{not in Vi}
 
 							*-U* *E230*
@@ -497,6 +507,13 @@ a slash.  Thus "-R" means recovery and "-/R" readonly.
 		":rv" or ":wv" are used.  See also |viminfo-file|.
 		{not in Vi}
 
+							*--clean*
+--clean		Equal to "-u DEFAULTS -i NONE":
+		- initializations from files and environment variables is
+		  skipped
+		- the |defaults.vim| script is loaded, which implies
+		  'nocompatible': use Vim defaults
+		- no viminfo file is read or written
 							*-x*
 -x		Use encryption to read/write files.  Will prompt for a key,
 		which is then stored in the 'key' option.  All writes will
@@ -868,6 +885,7 @@ accordingly.  Vim proceeds in this order:
 	Loading plugins won't be done when:
 	- The 'loadplugins' option was reset in a vimrc file.
 	- The |--noplugin| command line argument is used.
+	- The |--clean| command line argument is used.
 	- The "-u NONE" command line argument is used |-u|.
 	- When Vim was compiled without the |+eval| feature.
 	Note that using "-c 'set noloadplugins'" doesn't work, because the
@@ -990,6 +1008,7 @@ starts its initializations.  But as soon as:
 - a vimrc file in the current directory, or
 - the "VIMINIT" environment variable is set, or
 - the "-N" command line argument is given, or
+- the "--clean" command line argument is given, or
   even when no vimrc file exists.
 - the |defaults.vim| script is loaded, or
 - gvimrc file was found,

runtime/doc/usr_01.txt

@@ -1,4 +1,4 @@
-*usr_01.txt*	For Vim version 8.0.  Last change: 2010 Nov 03
+*usr_01.txt*	For Vim version 8.0.  Last change: 2017 Jul 15
 
 		     VIM USER MANUAL - by Bram Moolenaar
 
@@ -140,19 +140,19 @@ On other systems, you have to do a little work:
 
 1. Copy the tutor file.  You can do this with Vim (it knows where to find it):
 >
-	vim -u NONE -c 'e $VIMRUNTIME/tutor/tutor' -c 'w! TUTORCOPY' -c 'q'
+	vim --clean -c 'e $VIMRUNTIME/tutor/tutor' -c 'w! TUTORCOPY' -c 'q'
 <
    This will write the file "TUTORCOPY" in the current directory.  To use a
 translated version of the tutor, append the two-letter language code to the
 filename.  For French:
 >
-	vim -u NONE -c 'e $VIMRUNTIME/tutor/tutor.fr' -c 'w! TUTORCOPY' -c 'q'
+	vim --clean -c 'e $VIMRUNTIME/tutor/tutor.fr' -c 'w! TUTORCOPY' -c 'q'
 <
 2. Edit the copied file with Vim:
 >
-	vim -u NONE -c "set nocp" TUTORCOPY
+	vim --clean TUTORCOPY
 <
-   The extra arguments make sure Vim is started in a good mood.
+   The --clean argument makes sure Vim is started with nice defaults.
 
 3. Delete the copied file when you are finished with it:
 >