Default --die-when, and the Die On and Die When metadata.

docs/index.bs

@@ -577,22 +577,19 @@ so they're specified before the individual commands:
 	and things that look a little questionable but are totally okay to generate a document with are "warning".
 
 	The `--die-on` flag controls which sorts of errors
-	cause Bikeshed to immediately die
+	cause Bikeshed to fail to produce output
 	and exit with a non-0 status
 	(indicating the command failed).
 
 	Possible values are "nothing", "fatal", "link-error", "warning", and "everything",
 	with each level including all previous levels.
 	Defaults to "fatal".
 
-	It's often useful to set this to "nothing" if you just need to push thru and generate a spec,
-	or if you're generating a freshly-written or freshly-ported spec that may have several errors,
-	where it's useful to see all the errors at once,
-	in case some depend on each other.
+	It can sometimes be useful to set this to "nothing"
+	if you just need to push thru and generate a spec
+	that happens to throw some unimportant errors
+	you don't have time to fix.
 	The `-f` flag is a shorthand for this.
-	(Pairing this with `-q` or `-qq` might be useful,
-	to suppress the non-fatal errors temporarily
-	and make the output easier to read.)
 
 	Alternately, it can be useful to set it to a level stricter than "fatal"
 	if you want to ensure that,
@@ -604,6 +601,36 @@ so they're specified before the individual commands:
 	but is guaranteed to always die on *all* error messages,
 	even if more levels are added in the future.
 
+	Note that this can also be controlled from within your document
+	(or your group's metadata)
+	via the [=Die On=] metadata.
+
+: `--die-when = [ early | late ]`
+:: When Bikeshed encounters a disallowed error
+	(per the `--die-on` value),
+	it can either die *immediately*
+	(`early`)
+	so you can see the error and fix it
+	without the rest of the document potentially being incorrect
+	and throwing nonsensical errors;
+	or it can wait until the end of processing (`late`) to die,
+	so you can see all the errors
+	without having to continually rerun the command.
+
+	Either way, Bikeshed will exit with a non-zero status,
+	and refuse to actually produce an output document.
+
+	If unspecified, this defaults to `late`.
+
+	(If using `late`
+	and processing a document with many output messages,
+	it might be useful to temporarily run it with `-q` or `-qq`,
+	so you can focus on the more important messages first.)
+
+	Note that this can also be controlled from within your document
+	(or your group's metadata)
+	via the [=Die When=] metadata.
+
 : `-f` or `--force`
 :: A shorthand for `--die-on=nothing`.
 
@@ -1118,6 +1145,11 @@ Several keys are required information, and will cause the processor to flag an e
 There are several additional optional keys:
 
 <ul dfn-for=metadata export>
+	* <dfn>Die On</dfn> and <dfn>Die When</dfn>
+		give the same control that the `--die-on` and `--die-when` command-line options do.
+		They take the same values--
+		a single keyword--
+		as the corresponding command-line arguments.
 	* <dfn>H1</dfn> contains the text/markup that goes into the document's <{h1}> element.
 		If omitted, this defaults to the value of the [=metadata/Title=] metadata,
 		which is usually what you want.