docs: add pinned commit documentation

Signed-off-by:  Eric Callahan <arksine.code@gmail.com>

docs/changelog.md

@@ -40,14 +40,15 @@ The format is based on [Keep a Changelog].
 - **spoolman**:  Report spool ids set during a print in history auxiliary data
 - **sensor**: Added support for history fields reported in auxiliary data
 - **power**:  Added support for `uhubctl` devices
+- **update_manager**: Add support for pinned git commits
 
 ### Fixed
 
 - **simplyprint**:  Fixed import error preventing the component from loading.
 - **update_manager**: Moonraker will now restart the correct "moonraker" and
   "klipper" services if they are not the default values.
-- **job_queue**: Fixed transition wihen auto is disabled
+- **job_queue**: Fixed transition when auto is disabled
-- **history**: Added modification time to file existance checks.
+- **history**: Added modification time to file existence checks.
 - **dbus_manager**: Fixed PolKit warning when PolKit features are not used.
 - **job_queue**: Fixed a bug where the `job_transition_gcode` runs when the
   queue is started.  It will now only run between jobs during automatic

docs/configuration.md

@@ -1826,15 +1826,27 @@ enable_packagekit: True
 #   updates will be processed via PackageKit over D-Bus.  When set to False
 #   the "apt cli" fallback will be used.  The default is True.
 channel: dev
-#   The update channel applied to Klipper and Moonraker.  May dev or
+#   The update channel applied to Klipper and Moonraker.  May dev, beta or
-#   beta.  The dev channel will update to the latest commit pushed
+#   stable.  The dev channel will update to the latest commit pushed
 #   to the repo, whereas the beta channel will update to the latest
-#   commit tagged by Moonraker.  The beta channel will see less frequent
+#   commit tagged by Moonraker.  The beta and stable channels will see less
-#   updates and should be more stable.  Users on the beta channel will have
+#   frequent updates and should be more stable.  Users on the beta channel will
-#   more opportunity to review breaking changes before choosing to update.
+#   have more opportunity to review breaking changes before choosing to update.
 #   The default is dev.
 ```
 
+!!! Note
+    Configuration is automatically detected for Moonraker and Klipper, however
+    it is possible to override the `channel` and `pinned_commit` options on
+    a per application basis for each.  This can be done by specifying the
+    configuration in `moonraker.conf`.  For example:
+
+    ```ini
+    [update_manager klipper]
+    channel: dev
+    pinned_commit: 79930ed99a1fc284f41af5755908aa1fab948ce1
+    ```
+
 #### Extension Configuration
 The update manager may be configured manage additional software, henceforth
 referred to as "extensions".  In general terms, an extension may be defined
@@ -2050,6 +2062,14 @@ info_tags:
 #   Frontends my use these tags to perform additional actions or display
 #   information, see your extension documentation for details on configuration.
 #   The default is an empty list (no info tags).
+pinned_commit:
+#   A git commit hash to "pin" updates to.  When specified Moonraker will not
+#   update the repo beyond the pinned commit.  If the repo is already beyond
+#   the specified commit, or if the commit is not in the repo, futher updates
+#   are disabled until the pinned_commit is changed.  It is recommended to
+#   specify the complete hash, however abbreviated hashes with a minimum of
+#   8 characters are accepted.  The "pinned_commit" overrides the update
+#   behavior set by the "channel" option.  The default is no pinned commit.
 ```
 
 !!! Note