Log levels can now be specified with "[v1] " or "[v2] " substrings
that are then stripped and filtered at the final logger. This follows
our existing "[unexpected]" etc convention and doesn't require a
wholesale reworking of our logging at the moment.
cmd/tailscaled then gets a new --verbose=N flag to take a log level
that controls what gets logged to stderr (and thus systemd, syslog,
etc). Logtail is unaffected by --verbose.
This commit doesn't add annotations to any existing log prints. That
is in the next commit.
Updates #924
Updates #282
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Brad Fitzpatrick
57dd247376