Fix trailing slash in URL causing ValueError in add command (issue #1137)

Strip trailing slashes from VCS URLs at the entry point of vcs_url_to_purl
so that patterns like https://github.com/org/repo/ are normalised before
regex matching and path splitting. Add parametrized regression tests for
GitHub, Bitbucket, GitLab, and generic URLs with trailing slashes.

https://claude.ai/code/session_01HousmFCGC1BbEczgkmTSC6

Author: claude

dfetch/util/purl.py

@@ -114,6 +114,7 @@ def vcs_url_to_purl(
     Supports GitHub, Bitbucket, SVN, SSH paths, and generic VCS URLs.
     Optionally specify version and subpath.
     """
+    vcs_url = vcs_url.rstrip("/")
     purl = _known_purl_types(vcs_url, version, subpath)
     if purl:
         return purl

tests/test_purl.py

@@ -115,6 +115,18 @@
             "git://git.git.savannah.gnu.org/automake.git",
             "pkg:generic/automake?vcs_url=git://git.git.savannah.gnu.org/automake.git",
         ),
+        # Trailing slash – issue #1137
+        ("https://github.com/cpputest/cpputest/", "pkg:github/cpputest/cpputest"),
+        ("https://github.com/dfetch-org/dfetch/", "pkg:github/dfetch-org/dfetch"),
+        ("https://bitbucket.org/team/repo/", "pkg:bitbucket/team/repo"),
+        (
+            "https://gitlab.com/group/project/",
+            "pkg:generic/group/project?vcs_url=https://gitlab.com/group/project",
+        ),
+        (
+            "https://vcs.example.com/org/repo/",
+            "pkg:generic/example/org/repo?vcs_url=https://vcs.example.com/org/repo",
+        ),
     ],
 )
 def test_remote_url_to_purl(url, expected):