r146736 added an undocumented syntax and many bugs handling it. The
documented syntax is "... [mode] [fg [bg]] [show]", where it is critical
for reducing ambiguity and keeping things simple that the mode is
parsed first. r146736 added buggy support for "... [mode] [fg [bg]]
[show] [mode] [fg [bg]]". One error was that after for failing to set
a partially-supported graphics mode, argv[optind] remains pointing to
the mode so doesn't match the first [fg [bg]], so the setting is
attempted again, with slightly worse error handling.
Fix this by removing it (support for the trailing '[mode] [fg [bg]]')
and cleaning up. The cleanups are mostly to remove convolutions and
bugs that didn't work to handle the ambiguous syntax '[fg [bg]] [fg [bg]]'
when [mode] and [show] are not present. Globals were set to allow
repeating the color settings at the end. The functions that set the
colors earlier were misnamed from set* to get*. All that they "got" is
is settings from argv. They applied the settings to the kernel and
the globals.
Fix restoration of colors in revert() by restoring 2 after the mode
change. Colors should not need to be restored, but a bug in scteken
clobbers them on any mode change, including ones for restoration. Don't
move the restoration of the other 3. Teken doesn't clobber them on
mode changes because it doesn't support them at all (sc still supports
the border color, but only using a non-teken ioctl).
Add restoration of colors after a successful mode change to work around
the scteken bug there too. The bug was previously masked by the general
setting of colors at the end.
Fix a longstanding parsing/error handling bug by exiting almost immediately
after matching the [mode] arg but failing to set the mode. Just revert
if necessary. Don't return to continue parsing but do it wrong. This
bug caused spamming the output with a usage() message and exiting with
status 1 whenever [mode] is not present bug [fg [bg]] or [show]. The
exit code 1 was actualy an ambiguous internal code for failure to match
[mode] or failure to set [mode]. This 1 was obfuscated by spelling it
EXIT_FAILURE, but actual exit codes spell EXIT_FAILURE as 1. Remove
another global which could have been used to disambiguate this but was
only used to micro-optimize the (unnecessary except for other bugs)
setting of colors at the end.
1b8c842e06