update RELEASE to v0.50.2 with doc update (#5571)

Signed-off-by: t-kikuc <tkikuchi07f@gmail.com>
Signed-off-by: pipecd-bot <pipecd.dev@gmail.com>

Author: t-kikuc

RELEASE

@@ -1,6 +1,6 @@
 # Generated by `make release` command.
 # DO NOT EDIT.
-tag: v0.50.1
+tag: v0.50.2
 
 releaseNoteGenerator:
   showCommitter: false

docs/content/en/docs-v0.50.x/user-guide/plan-preview.md

@@ -38,7 +38,8 @@ pipectl plan-preview \
   --repo-remote-url={ REPO_REMOTE_GIT_SSH_URL } \
   --head-branch={ HEAD_BRANCH } \
   --head-commit={ HEAD_COMMIT } \
-  --base-branch={ BASE_BRANCH }
+  --base-branch={ BASE_BRANCH } \
+  --sort-label-keys={ SORT_LABEL_KEYS }
 ```
 
 You can run it locally or integrate it to your CI system to run automatically when a new pull request is opened/updated. Use `--help` to see more options.
@@ -47,6 +48,13 @@ You can run it locally or integrate it to your CI system to run automatically wh
 pipectl plan-preview --help
 ```
 
+### Order of the results
+
+By default, the results are sorted by PipedID and Application Name.
+
+If you want to sort the results by labels, add `--sort-label-keys` option. For example, when you run with `--sort-label-keys=env,team`, the results will be sorted by PipedID, `env` label, `team` label, and then Application Name.
+
+
 ## GitHub Actions
 
 If you are using GitHub Actions, you can seamlessly integrate our prepared [actions-plan-preview](https://github.com/pipe-cd/actions-plan-preview) to your workflows. This automatically comments the plan-preview result on the pull request when it is opened or updated. You can also trigger to run plan-preview manually by leave a comment `/pipecd plan-preview` on the pull request.