fix: git links in comments for multiple OIDs

The chance of finding multiple object IDs when performing lookups with
a shortened SHA1 hash (7 digits) seems to be quite high.

In those cases pygit2 will throw an error.
Let's catch those exceptions and gracefully handle them.

Fixes: aurweb-errors#496 (and alike)
Signed-off-by: moson <moson@archlinux.org>

aurweb/scripts/rendercomment.py

@@ -72,8 +72,13 @@ class GitCommitsInlineProcessor(markdown.inlinepatterns.InlineProcessor):
 
     def handleMatch(self, m, data):
         oid = m.group(1)
-        if oid not in self._repo:
-            # Unknown OID; preserve the orginal text.
+        # Lookup might raise ValueError in case multiple object ID's were found
+        try:
+            if oid not in self._repo:
+                # Unknown OID; preserve the orginal text.
+                return None, None, None
+        except ValueError:
+            # Multiple OID's found; preserve the orginal text.
             return None, None, None
 
         el = Element("a")

test/test_rendercomment.py

@@ -1,5 +1,7 @@
+import os
 from unittest import mock
 
+import pygit2
 import pytest
 
 from aurweb import aur_logging, config, db, time
@@ -166,6 +168,43 @@ http://example.com/{commit_hash}\
     assert comment.RenderedComment == expected
 
 
+def test_git_commit_link_multiple_oids(
+    git: GitRepository, user: User, package: Package
+):
+    # Make sure we get reproducible hashes by hardcoding the dates
+    date = "Sun, 16 Jul 2023 06:06:06 +0200"
+    os.environ["GIT_COMMITTER_DATE"] = date
+    os.environ["GIT_AUTHOR_DATE"] = date
+
+    # Package names that cause two object IDs starting with "09a3468"
+    pkgnames = [
+        "bfa3e330-23c5-11ee-9b6c-9c2dcdf2810d",
+        "54c6a420-23c6-11ee-9b6c-9c2dcdf2810d",
+    ]
+
+    # Create our commits
+    for pkgname in pkgnames:
+        with db.begin():
+            package = db.create(
+                Package, PackageBase=package.PackageBase, Name=pkgname, Version="1.0"
+            )
+        git.commit(package, pkgname)
+
+    repo_path = config.get("serve", "repo-path")
+    repo = pygit2.Repository(repo_path)
+
+    # Make sure we get an error when we search the git repo for "09a3468"
+    with pytest.raises(ValueError) as oid_error:
+        assert "09a3468" in repo
+        assert "ambiguous OID prefix" in oid_error
+
+    # Create a comment, referencing "09a3468"
+    comment = create_comment(user, package.PackageBase, "Commit 09a3468 is nasty!")
+
+    # Make sure our comment does not contain a link.
+    assert comment.RenderedComment == "<p>Commit 09a3468 is nasty!</p>"
+
+
 def test_flyspray_issue_link(user: User, pkgbase: PackageBase):
     text = """\
 FS#1234567.