allow min pre release versions to be set

src/delete.ts

@@ -19,12 +19,22 @@ export function getVersionIds(input: Input): Observable<string[]> {
       map(versionInfo => {
         const numberVersionsToDelete =
           versionInfo.length - input.minVersionsToKeep
-        return numberVersionsToDelete <= 0
-          ? []
-          : versionInfo
-              .filter(info => !input.ignoreVersions.test(info.version))
-              .map(info => info.id)
-              .slice(0, numberVersionsToDelete)
+
+        if (input.deletePreReleaseVersions == 'true') {
+          return numberVersionsToDelete <= 0
+            ? []
+            : versionInfo
+                .filter(info => !input.ignoreVersions.test(info.version))
+                .map(info => info.id)
+                .slice(0, -input.minVersionsToKeep)
+        } else {
+          return numberVersionsToDelete <= 0
+            ? []
+            : versionInfo
+                .filter(info => !input.ignoreVersions.test(info.version))
+                .map(info => info.id)
+                .slice(0, numberVersionsToDelete)
+        }
       })
     )
   }

src/input.ts

@@ -47,8 +47,9 @@ export class Input {
     this.token = validatedParams.token
 
     if (this.deletePreReleaseVersions == 'true') {
-      this.numOldVersionsToDelete = 100
-      this.minVersionsToKeep = 0
+      this.numOldVersionsToDelete = 100 - this.minVersionsToKeep
+      this.minVersionsToKeep =
+        this.minVersionsToKeep > 0 ? this.minVersionsToKeep : 1
       this.ignoreVersions = new RegExp('^(0|[1-9]\\d*)((\\.(0|[1-9]\\d*))*)$')
     }
   }

src/main.ts

@@ -16,7 +16,9 @@ function getActionInput(): Input {
     numOldVersionsToDelete: Number(getInput('num-old-versions-to-delete')),
     minVersionsToKeep: Number(getInput('min-versions-to-keep')),
     ignoreVersions: RegExp(getInput('ignore-versions')),
-    deletePreReleaseVersions: getInput('delete-only-pre-release-versions'),
+    deletePreReleaseVersions: getInput(
+      'delete-only-pre-release-versions'
+    ).toLowerCase(),
     token: getInput('token')
   })
 }