Bug#531647: Vim filters through indent when -cindent and equalprg unset

[Bram Moolenaar]

James -

> Using = when Vim was built with -cindent and the user hasn't set
> 'equalprg' filters the text through the external command `indent'.  As
> this behavior isn't documented, it's a surprise to the user and can
> cause the text-to-be-indented to be deleted or replaced with error
> messages from the shell.

This is old Vi behavior, AFAIK.

> The attached patch is a proposed solution which instead emits an error
> telling the user that 'equalprg' needs to be set.  I've added the
> explanation to ='s help as well, with a help tag for the new error
> number.

I don't think changing the behavior is a good idea.  I'll add a comment
at 'equalprg' about what happens when it's empty.  And in change.txt:

={motion}		Filter {motion} lines through the external program
			given with the 'equalprg' option.  When the 'equalprg'
			option is empty (this is the default), use the
			internal formatting function |C-indenting|.  But when
			'indentexpr' is not empty, it will be used instead
			|indent-expression|.  When Vim was compiled without
			internal formatting then the "indent" program is used
			as a last resort.

- Bram

-- 
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