flux-job(1): add subsection for flux job info

Problem: flux job info is not documented.

Add a new subsection for it.

doc/man1/flux-job.rst

@@ -312,6 +312,53 @@ Inactive jobs may also be purged automatically if the job manager is
 configured as described in :man5:`flux-config-job-manager`.
 
 
+flux job info
+-------------
+
+The :command:`flux job info` retrieves the selected low level job artifact
+and displays it on standard output.  The following keys are valid:
+
+eventlog
+   The primary job eventlog, consisting of timestamped events that drive the
+   job through various states.  For example, a job that is pending resource
+   allocation in SCHED state transitions to RUN state on the *alloc* event.
+
+   See also :doc:`rfc:spec_18` and :doc:`rfc:spec_21`.
+
+guest.exec.eventlog
+   The execution eventlog, consisting of timestamped events posted by the
+   execution system while the job is running.
+
+guest.input, guest.output
+   The job input and output eventlogs, consisting of timestamped chunks of
+   input/output data.
+
+   See also :doc:`rfc:spec_24`.
+
+jobspec
+   The job specification.  Three versions are available:
+
+   - default: the *current* jobspec, which may reflect updates,
+     for example if the job duration was extended
+
+   - with :option:`--original`: the original jobspec submitted by the user
+
+   - with :option:`--base`: the jobspec as initially ingested to the KVS, after
+     the frobnicator filled in any default values, but before updates
+
+   See also :doc:`rfc:spec_25` and :doc:`rfc:spec_14`.
+
+R
+   The resource set allocated to the job.  Two versions are available:
+
+   - default: the *current* R, which may reflect updates, for example if the job
+     expiration time was extended (default)
+
+   - with :option:`--base`: the initial R allocated by the scheduler
+
+   See also :doc:`rfc:spec_20`.
+
+
 RESOURCES
 =========