Fix bugs with multiple configured remotes; debug-log return code

Pull Request: #18 (main)

git-grok

@@ -525,7 +525,22 @@ class Main:
     # Returns current git folder remote (most often "origin").
     #
     def git_get_current_remote(self) -> str:
-        return self.shell(["git", "remote", "show"])
+        [_, symbolic_ref, _] = self.shell_no_throw(
+            ["git", "symbolic-ref", "-q", "HEAD"]
+        )
+        if not symbolic_ref:
+            raise UserException(
+                'To run git-grok, you must be on a branch. Check your "git status".'
+            )
+        upstream = self.shell(
+            ["git", "for-each-ref", "--format=%(upstream:short)", symbolic_ref]
+        )
+        m = re.match(r"([^/]+)/.+$", upstream)
+        if not m:
+            raise UserException(
+                f'Cannot extract remote from upstream "{upstream}" of symbolic ref "{symbolic_ref}".'
+            )
+        return m.group(1)
 
     #
     # Returns the current remote branch name on GitHub.