Although our use of ANSI codes here is rather simple it is generally good
practice to use terminfo in order to be portable to different terminal
emulators.
Vendor github.com/Nvveen/Gotty (actually my fork with a fix, see
https://github.com/Nvveen/Gotty/pull/1) and use that to parse the terminfo
files.
Note that "\e]2K" (clear entire line) is not covered by terminfo. We can
achieve the same end by first clearing from begining of line to cursor
(el1="\e]1K") and then clearing from cursor to end of line (el="\e]k").
Test suite has been updated and forces (either directly or by setting $TERM to
something highly unlikely to exist) the use of the non-terminfo fallbacks which
retains the same output behaviour as previously. This is preferable even to
relying on a well-known and relatively static terminfo (like vt102) since even
that in principal might have different terminfo encodings.
In case terminfo is not available at all for $TERM or doesn't expose the
specific capabilities which we use then fall back to the previous manual
escapes, with the exception that we avoid "\e]2K" as discussed above.
Tested with a manual docker pull with rxvt-unicode ($TERM=rxvt-unicode), xterm
($TERM=xterm), mlterm ($TERM=mlterm) and aterm ($TERM=kterm).
Signed-off-by: Ian Campbell <ian.campbell@docker.com>
