Add --dry-run to preview changes to PR (#26)

Justfile

@@ -45,6 +45,11 @@ release *OPTIONS:
     git-check --check-repo=1 {{SETUP_BEND_PATH}}; \
     make-release {{OPTIONS}}
 
+# Set milestone for PR in dry-run mode
+dry-run *OPTIONS:
+  @overlay use {{ join(SETUP_BEND_PATH, 'nu', 'milestone.nu') }}; \
+  milestone-update --dry-run {{OPTIONS}}
+
 # Plugins need to be registered only once after nu v0.61
 _setup:
   @register -e json {{ join(NU_DIR, _query_plugin) }}

nu/milestone.nu

@@ -19,17 +19,26 @@ export def 'milestone-update' [
   --milestone(-m): string,  # Milestone name
   --pr: string,             # The PR number/url/branch of the PR that we want to add milestone.
   --force(-f),              # Force update milestone even if the milestone is already set.
+  --dry-run(-d),            # Dry run, only print the milestone that would be set.
 ] {
   if not (is-installed 'gh') {
     print 'gh command not found, please install it first, see: https://cli.github.com/.'
     exit $ECODE.MISSING_BINARY
   }
   if ($gh_token | is-not-empty) { $env.GH_TOKEN = $gh_token }
   let selected = if ($milestone | is-empty) { guess-milestone $repo $pr } else { $milestone }
-  if $force { gh pr edit $pr --repo $repo --remove-milestone }
-  print $'(char nl)Setting milestone to (ansi p)($selected)(ansi reset) for PR ($pr) in repository ($repo)...'
+  if $force {
+    if $dry_run {
+      print $'(char nl)Would remove milestone for PR (ansi p)($pr)(ansi reset) in repository (ansi p)($repo)(ansi reset) ...'
+    } else {
+      gh pr edit $pr --repo $repo --remove-milestone
+    }
+  }
+  print $'(char nl)Setting milestone to (ansi p)($selected)(ansi reset) for PR (ansi p)($pr)(ansi reset) in repository (ansi p)($repo)(ansi reset) ...'
   # FIXME: GraphQL: Resource not accessible by integration (updatePullRequest)
-  gh pr edit $pr --repo $repo --milestone $selected
+  if not $dry_run {
+    gh pr edit $pr --repo $repo --milestone $selected
+  }
 }
 
 # Guess milestone by the merged date of the PR and the infomation of open milestones.