🚀 [Feature]: Add target branch detection to prevent releases from non-default branch merges (#7)

The action now detects whether a pull request targets the repository's
default branch and uses this to determine the correct release type.
Releases and site deployments are only triggered when PRs are merged
into the default branch, preventing accidental releases from feature
branch merges.

## Target branch detection

Added detection logic to identify the PR's target branch and compare it
against the repository's default branch:

- `targetBranch` - Extracted from the PR's base ref
(`pullRequest.Base.Ref`)
- `defaultBranch` - Retrieved from repository info
(`eventData.Repository.default_branch`)
- `isTargetDefaultBranch` - Boolean flag indicating whether the PR
targets the default branch

## ReleaseType logic update

The `ReleaseType` calculation now factors in the target branch:

| Condition | ReleaseType |
|-----------|-------------|
| PR merged to **default** branch | `Release` |
| PR merged to **non-default** branch | `None` |
| PR closed without merge | `Cleanup` |
| Open PR with prerelease label | `Prerelease` |
| Everything else | `None` |

This ensures that PRs merged into feature branches or other non-default
branches do not trigger releases.

## Site publishing update

The `PublishSite` condition now also requires the PR to be merged into
the default branch (`$isMergedPR -and $isTargetDefaultBranch`), ensuring
sites are only deployed when merging to the main branch.

## Code simplification

Simplified the event data extraction by removing defensive null-checking
in favor of relying on `Get-GitHubEventData` to provide valid data. The
action now uses direct property access for cleaner, more readable code.

## Logging improvements

The GitHub event inputs logging now includes branch information for
debugging:

```
TargetBranch          : main
DefaultBranch         : main
IsTargetDefaultBranch : True
```

Author: MariusStorhaug

scripts/main.ps1

@@ -195,47 +195,27 @@ $settings | Add-Member -MemberType NoteProperty -Name WorkingDirectory -Value $w
 
 # Calculate job run conditions
 LogGroup 'Calculate Job Run Conditions:' {
-    # Common conditions
-    $eventData = $null
-    try {
-        $eventData = Get-GitHubEventData -ErrorAction Stop
-    } catch {
-        if (-not [string]::IsNullOrEmpty($env:GITHUB_EVENT_PATH) -and (Test-Path -Path $env:GITHUB_EVENT_PATH)) {
-            $eventData = Get-Content -Path $env:GITHUB_EVENT_PATH -Raw | ConvertFrom-Json
-        }
-    }
+    $eventData = Get-GitHubEventData -ErrorAction Stop
 
     LogGroup 'GitHub Event Data' {
-        if ($null -ne $eventData) {
-            Write-Host ($eventData | ConvertTo-Json -Depth 10 | Out-String)
-        } else {
-            Write-Host 'No event data available.'
-        }
-    }
-
-    $pullRequestAction = if ($null -ne $eventData.Action) {
-        $eventData.Action
-    } else {
-        $env:GITHUB_EVENT_ACTION
-    }
-
-    $pullRequest = if ($null -ne $eventData.PullRequest) {
-        $eventData.PullRequest
-    } else {
-        $null
+        $eventData | ConvertTo-Json -Depth 10 | Out-String
     }
 
-    $pullRequestIsMerged = if ($null -ne $pullRequest -and $null -ne $pullRequest.Merged) {
-        [bool]$pullRequest.Merged
-    } else {
-        $false
-    }
+    $pullRequestAction = $eventData.Action
+    $pullRequest = $eventData.PullRequest
+    $pullRequestIsMerged = $pullRequest.Merged
+    $targetBranch = $pullRequest.Base.Ref
+    $defaultBranch = $eventData.Repository.default_branch
+    $isTargetDefaultBranch = $targetBranch -eq $defaultBranch
 
     Write-Host 'GitHub event inputs:'
     [pscustomobject]@{
         GITHUB_EVENT_NAME                = $env:GITHUB_EVENT_NAME
         GITHUB_EVENT_ACTION              = $pullRequestAction
         GITHUB_EVENT_PULL_REQUEST_MERGED = $pullRequestIsMerged
+        TargetBranch                     = $targetBranch
+        DefaultBranch                    = $defaultBranch
+        IsTargetDefaultBranch            = $isTargetDefaultBranch
     } | Format-List | Out-String
 
     $isPR = $env:GITHUB_EVENT_NAME -eq 'pull_request'
@@ -254,10 +234,13 @@ LogGroup 'Calculate Job Run Conditions:' {
 
     # Determine ReleaseType - single source of truth for what Publish-PSModule should do
     # Values: 'Release', 'Prerelease', 'Cleanup', 'None'
+    # Release only happens when PR is merged into the default branch
     $releaseType = if (-not $isPR) {
         'None'
-    } elseif ($isMergedPR) {
+    } elseif ($isMergedPR -and $isTargetDefaultBranch) {
         'Release'
+    } elseif ($isMergedPR -and -not $isTargetDefaultBranch) {
+        'None'  # Merged to non-default branch - no release
     } elseif ($isAbandonedPR) {
         'Cleanup'
     } elseif ($shouldPrerelease) {
@@ -267,13 +250,14 @@ LogGroup 'Calculate Job Run Conditions:' {
     }
 
     [pscustomobject]@{
-        isPR              = $isPR
-        isOpenOrUpdatedPR = $isOpenOrUpdatedPR
-        isAbandonedPR     = $isAbandonedPR
-        isMergedPR        = $isMergedPR
-        isNotAbandonedPR  = $isNotAbandonedPR
-        shouldPrerelease  = $shouldPrerelease
-        ReleaseType       = $releaseType
+        isPR                  = $isPR
+        isOpenOrUpdatedPR     = $isOpenOrUpdatedPR
+        isAbandonedPR         = $isAbandonedPR
+        isMergedPR            = $isMergedPR
+        isNotAbandonedPR      = $isNotAbandonedPR
+        isTargetDefaultBranch = $isTargetDefaultBranch
+        shouldPrerelease      = $shouldPrerelease
+        ReleaseType           = $releaseType
     } | Format-List | Out-String
 }
 
@@ -467,7 +451,7 @@ LogGroup 'Calculate Job Run Conditions:' {
         ReleaseType          = $releaseType  # 'Release', 'Prerelease', 'Cleanup', or 'None'
         BuildDocs            = $isNotAbandonedPR -and (-not $settings.Build.Docs.Skip)
         BuildSite            = $isNotAbandonedPR -and (-not $settings.Build.Site.Skip)
-        PublishSite          = $isMergedPR
+        PublishSite          = $isMergedPR -and $isTargetDefaultBranch
     }
     $settings | Add-Member -MemberType NoteProperty -Name Run -Value $run