feat(git): add get tag message function

Author: LuisHenri

commitizen/git.py

@@ -83,7 +83,7 @@ def from_line(cls, line: str, inner_delimiter: str) -> GitTag:
 
 
 def tag(
-    tag: str, annotated: bool = False, signed: bool = False, msg: Optional[str] = None
+    tag: str, annotated: bool = False, signed: bool = False, msg: str | None = None
 ) -> cmd.Command:
     _opt = ""
     if annotated:
@@ -203,6 +203,13 @@ def get_latest_tag_name() -> str | None:
     return c.out.strip()
 
 
+def get_tag_message(tag: str) -> str | None:
+    c = cmd.run(f"git tag -l --format='%(contents:subject)' {tag}")
+    if c.err:
+        return None
+    return c.out.strip()
+
+
 def get_tag_names() -> list[str | None]:
     c = cmd.run("git tag --list")
     if c.err: