action: Generalize new revision check

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>

Author: carlescufi

action.py

@@ -127,7 +127,7 @@ def is_sha(rev):
 
     return len(rev) == 40
 
-def is_impostor(repo, rev):
+def is_valid_rev(repo, rev, check_impostor):
 
     def compare(base, head):
         try:
@@ -138,32 +138,29 @@ def compare(base, head):
                    log(f"No common ancestor between {base} and {head}")
                    return False
             else:
-                log(f'compare: GithubException: {e}')
+                log(f'check_rev: compare: GithubException: {e}')
                 raise
-        return c.status in ('behind', 'identical')
+        status_ok = ('behind', 'identical') if is_sha(head) else ('identical')
+        return c.status in status_ok
 
     if not rev:
-        log('is_impostor: revision is None')
-        return True
-
-    if not is_sha(rev):
-        log('is_impostor: not a SHA')
+        log('check_rev: rev is None')
         return False
 
     try:
         for b in repo.get_branches():
             if compare(f'refs/heads/{b.name}', rev):
-                log(f'Found revision {rev} in branch {b.name}')
-                return False
+                log(f'check_rev: Found revision {rev} in branch {b.name}')
+                return True
         for t in repo.get_tags():
             if compare(f'refs/tags/{t.name}', rev):
-                log(f'Found revision {rev} in tag {t.name}')
-                return False
+                log(f'check_rev: Found revision {rev} in tag {t.name}')
+                return True
     except GithubException as e:
-        log(f'is_impostor: GithubException: {e}')
-        return True
+        log(f'check_rev: GithubException: {e}')
+        return False
 
-    return True
+    return False
 
 def fmt_rev(repo, rev):
     if not rev: