add another unknownRevision error

The following error also caused blame not working:

> git rev-parse --symbolic-full-name my_branch@{u}
fatal: upstream branch 'refs/heads/my_branch' not stored as a remote-tracking branch

src/git/git.ts

@@ -62,7 +62,7 @@ const GitWarnings = {
     foundButNotInRevision: /Path \'.*?\' exists on disk, but not in/i,
     headNotABranch: /HEAD does not point to a branch/i,
     noUpstream: /no upstream configured for branch \'(.*?)\'/i,
-    unknownRevision: /ambiguous argument \'.*?\': unknown revision or path not in the working tree/i
+    unknownRevision: /ambiguous argument \'.*?\': unknown revision or path not in the working tree|not stored as a remote-tracking branch/i
 };
 
 async function gitCommand(options: CommandOptions & { readonly correlationKey?: string }, ...args: any[]): Promise<string> {
@@ -646,4 +646,4 @@ export class Git {
 
         return gitCommand({ cwd: repoPath }, ...params);
     }
-}
+}