When multiple notification targets are configured only the first target received notification message content. The subsequent targets would read EOF when trying to read the content. Fix this issue and add regression test coverage for it, exercising existing test code with a gotd.conf file which contains two notification targets.

ok op@

This leak resulted in the gotd notify process spinning on CPU in an imsg_read() -> EAGAIN loop once it ran out of file descriptors.

pointed out by op@

Ephermeral processes on the other end of a pipe might decide to exit which results in EPIPE when writing. This is not a fatal error but is somewhat expected during normal operation (at least until we improve the inter-process communication about notifications).

Was suggested by Lucas some time ago. ok stsp@ with a tweak in the manual.

ok stsp

ok stsp

ok stsp@

Now that gotd has the start of helpers, got-notify-email is the first. This is still behind the --enable-gotd flag.

At present only email notifications are implemented. Code for HTTP notifications is not yet finished, hence HTTP-related documentation remains hidden for now. This adds a new 'notify' process which has an "exec" pledge. It runs helper programs which implement the notification transport layer, such as got-notify-email which speaks SMTP. This design avoids having to link all of gotd with network libraries and related crypto libraries. Notification content is generated by the 'repo_write' process. Commit log messages and diffstats are written to a file which the 'notify' process will pass on to its helpers on stdin. The default output looks similar to 'got log -d'. If too many new commits are present the output looks similar to 'got log -s' instead. Tags always look like 'got tag -l'. The session process coordinates generation of notifications. It maintains a notification queue which holds one notification per updated reference, and passes notification requests from this queue to the 'repo_write' process for notification content creation and then to the 'notify' process for notification delivery. Only one notification can be in flight at a time to avoid file descriptor starvation if many references get updated in a single client session. ok op@