ref: document dvc exp clean (#4347)

* ref: document `dvc exp clean`

* review fixes

content/docs/command-reference/exp/clean.md

@@ -0,0 +1,33 @@
+# exp clean
+
+Cleanup DVC experiment temporary files.
+
+## Synopsis
+
+```usage
+usage: dvc exp clean [-h] [-q | -v]
+```
+
+## Description
+
+Runs housekeeping tasks within the <abbr>DVC repository</abbr>, such as removing
+outdated internal experiments queue message files (to reduce disk space and
+improve performance).
+
+This is done automatically when running [queued experiments]. Running
+`dvc exp clean` manually should not be required for typical use cases, but it
+may be needed in the event that a queue worker unexpectedly crashed, or was
+forcefully killed by something other than DVC commands.
+
+[queued experiments]:
+  /doc/user-guide/experiment-management/running-experiments#the-experiments-queue
+
+## Options
+
+- `-h`, `--help` - shows the help message and exit.
+
+- `-q`, `--quiet` - do not write anything to standard output. Exit with 0 if no
+  problems arise, otherwise 1.
+
+- `-v`, `--verbose` - displays detailed tracing information from executing the
+  `dvc exp clean` command.

content/docs/command-reference/exp/index.md

@@ -9,17 +9,18 @@ A set of commands to generate and manage <abbr>experiments</abbr>:
 [apply](/doc/command-reference/exp/apply),
 [branch](/doc/command-reference/exp/branch),
 [remove](/doc/command-reference/exp/remove),
-[gc](/doc/command-reference/exp/gc), [push](/doc/command-reference/exp/list),
-[pull](/doc/command-reference/exp/pull), and
-[list](/doc/command-reference/exp/list).
+[gc](/doc/command-reference/exp/gc), [push](/doc/command-reference/exp/push),
+[pull](/doc/command-reference/exp/pull),
+[list](/doc/command-reference/exp/list), and
+[clean](/doc/command-reference/exp/clean).
 
 > Requires that Git is being used to version the project.
 
 ## Synopsis
 
 ```usage
 usage: dvc exp [-h] [-q | -v]
-          {show,apply,diff,run,gc,branch,list,push,pull,remove,init}
+          {show,apply,diff,run,gc,branch,list,push,pull,remove,init,clean}
           ...
 
 positional arguments:
@@ -37,6 +38,7 @@ positional arguments:
     gc                  Garbage collect unneeded experiments.
     push                Push a local experiment to a Git remote.
     pull                Pull an experiment from a Git remote.
+    clean               Cleanup dvc exp internal tempfiles.
 ```
 
 ## Description

content/docs/sidebar.json

@@ -245,6 +245,10 @@
             "label": "exp branch",
             "slug": "branch"
           },
+          {
+            "label": "exp clean",
+            "slug": "clean"
+          },
           {
             "label": "exp diff",
             "slug": "diff"