integrations: Remove deprecated !avatar syntax from git integration.

The !avatar() markdown syntax was removed from Zulip some time ago, 
but was still being used in the git integration. This commit replaces all 
remaining uses with plain text formatting.

Fixes: #632

Author: taylornlane

zulip/integrations/git/post-receive

@@ -47,7 +47,7 @@ def git_commit_range(oldrev: str, newrev: str) -> str:
         if hasattr(config, "format_commit_message"):
             commits += config.format_commit_message(author_email, subject, commit_id)
         else:
-            commits += f"!avatar({author_email}) {subject}\n"
+            commits += f"* {subject} (by {author_email})\n"
     return commits
 
 

zulip/integrations/git/zulip_git_config.py

@@ -36,9 +36,9 @@ def commit_notice_destination(repo: str, branch: str, commit: str) -> Optional[D
 # common customization is to include a link to the commit in your
 # graphical repository viewer, e.g.
 #
-# return '!avatar(%s) [%s](https://example.com/commits/%s)\n' % (author, subject, commit_id)
+# return '* [%s](https://example.com/commits/%s) (by %s)\n' % (subject, commit_id, author)
 def format_commit_message(author: str, subject: str, commit_id: str) -> str:
-    return f"!avatar({author}) {subject}\n"
+    return f"* {subject} (by {author})\n"
 
 
 ## If properly installed, the Zulip API should be in your import