As of forgejo/forgejo#2869, console logging implements three adaptations
for running forgejo under systemd/journald:
- forgejo learned to emit printk-style log level prefixes that are
picked up by journald and saved as the severity level of this line
(e.g., `<3>some text\n` means that "some text" will be saved as an
error entry);
- forgejo learned a new pseudo-flag "journaldflags" which is supposed to
replace "stdflags" when running under journald to reduce log clutter
(specifically, it removes date/time from log entries since the
time information is automatically saved by journald and displayed by
journalctl, and replaces the textual log level by the above-described
machine-parsable log level prefix);
- finally, forgejo will try to automatically detect whether it is
running under journald by parsing `$JOURNAL_STREAM` environment
variable and use "journalflags" as default flags if that is the case).
Document those.
Signed-off-by: Ivan Shapovalov <intelfx@intelfx.name>
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