fix: pylock.toml + git dependency => lock failure.

Fixes #3694

Signed-off-by: Frost Ming <[email protected]>

Author: frostming

news/3694.bugfix.md

@@ -0,0 +1 @@
+Ignore `packages.vcs.requested-revision` if it's None when formatting pylock.toml.

src/pdm/formats/pylock.py

@@ -42,9 +42,10 @@ def make_package(self, package: Package) -> dict[str, Any]:
             result["vcs"] = {
                 "type": req.vcs,
                 "url": req.repo,
-                "requested-revision": req.ref,
                 "commit-id": candidate.get_revision(),
             }
+            if req.ref:
+                result["vcs"]["requested-revision"] = req.ref
             if req.subdirectory:
                 result["vcs"]["subdirectory"] = req.subdirectory
         elif isinstance(req, FileRequirement):