Make use of git branch --show-current to retrieve branch

Author: fourjr

CHANGELOG.md

@@ -20,6 +20,10 @@ however, insignificant breaking changes do not guarantee a major version bump, s
 
 - Mentioned `competing` as an activity type. ([PR #2902](https://github.com/kyb3r/modmail/pull/2902))
 
+### Internal
+
+- Make use of `git branch --show-current` to retrieve branch insteasd of using prerelease version check.
+
 # v3.7.13
 
 ### Fixed

core/changelog.py

@@ -1,4 +1,6 @@
+import asyncio
 import re
+from subprocess import PIPE
 from typing import List
 
 from discord import Embed
@@ -167,7 +169,17 @@ async def from_url(cls, bot, url: str = "") -> "Changelog":
         Changelog
             The newly created `Changelog` parsed from the `url`.
         """
-        branch = "master" if not bot.version.is_prerelease else "development"
+        # get branch via git cli if available
+        proc = await asyncio.create_subprocess_shell(
+            "git branch --show-current", stderr=PIPE, stdout=PIPE,
+        )
+        err = await proc.stderr.read()
+        err = err.decode("utf-8").rstrip()
+        res = await proc.stdout.read()
+        branch = res.decode("utf-8").rstrip()
+        if not branch or err:
+            branch = "master" if not bot.version.is_prerelease else "development"
+
         url = url or f"https://raw.githubusercontent.com/kyb3r/modmail/{branch}/CHANGELOG.md"
 
         async with await bot.session.get(url) as resp: