Fix a bug about "discard all changes"

- Show the number of (not pushed) commits discarded.

pass/Models/PasswordStore.swift

@@ -605,7 +605,8 @@ class PasswordStore {
         storeRepository = nil
     }
     
-    func reset() throws {
+    // return the number of discarded commits 
+    func reset() throws -> Int {
         // get the remote origin/master branch
         guard let remoteBranches = try storeRepository?.remoteBranches(),
             let index = remoteBranches.index(where: { $0.shortName == "master" })
@@ -618,9 +619,8 @@ class PasswordStore {
         // get a list of local commits
         if let localCommits = try storeRepository?.localCommitsRelative(toRemoteBranch: remoteMasterBranch),
             localCommits.count > 0 {
-            //print("PasswordStore.reset: \(localCommits.count)")
-            // get the first local commit
-            guard let firstLocalCommit = localCommits.first,
+            // get the oldest local commit
+            guard let firstLocalCommit = localCommits.last,
                 firstLocalCommit.parents.count == 1,
                 let newHead = firstLocalCommit.parents.first else {
                     throw NSError(domain: "me.mssun.pass.error", code: 1, userInfo: [NSLocalizedDescriptionKey: "Cannot decide how to reset."])
@@ -629,9 +629,9 @@ class PasswordStore {
             self.updatePasswordEntityCoreData()
             NotificationCenter.default.post(Notification(name: Notification.Name("passwordUpdated")))
             self.setAllSynced()
+            return localCommits.count
         } else {
-            //print("PasswordStore.reset: no new commit")
-            return;  // no new commit
+            return 0  // no new commit
         }
     }
 }