git: verify commit user is set (#5754)

dvc/scm/git/backend/dulwich.py

@@ -182,11 +182,16 @@ class DulwichBackend(BaseGitBackend):  # pylint:disable=abstract-method
     def commit(self, msg: str, no_verify: bool = False):
         from dulwich.errors import CommitError
         from dulwich.porcelain import commit
+        from dulwich.repo import InvalidUserIdentity
 
         try:
             commit(self.root_dir, message=msg, no_verify=no_verify)
         except CommitError as exc:
             raise SCMError("Git commit failed") from exc
+        except InvalidUserIdentity as exc:
+            raise SCMError(
+                "Git username and email must be configured"
+            ) from exc
 
     def checkout(
         self,
@@ -528,6 +533,8 @@ class DulwichBackend(BaseGitBackend):  # pylint:disable=abstract-method
         message: Optional[str] = None,
         include_untracked: Optional[bool] = False,
     ) -> Tuple[Optional[str], bool]:
+        from dulwich.repo import InvalidUserIdentity
+
         from dvc.scm.git import Stash
 
         if include_untracked or ref == Stash.DEFAULT_STASH:
@@ -537,7 +544,12 @@ class DulwichBackend(BaseGitBackend):  # pylint:disable=abstract-method
 
         stash = self._get_stash(ref)
         message_b = message.encode("utf-8") if message else None
-        rev = stash.push(message=message_b)
+        try:
+            rev = stash.push(message=message_b)
+        except InvalidUserIdentity as exc:
+            raise SCMError(
+                "Git username and email must be configured"
+            ) from exc
         return os.fsdecode(rev), True
 
     def _stash_apply(self, rev: str):

dvc/scm/git/backend/pygit2.py

@@ -80,6 +80,15 @@ class Pygit2Backend(BaseGitBackend):  # pylint:disable=abstract-method
 
         return RefdbFsBackend(self.repo)
 
+    @property
+    def default_signature(self):
+        try:
+            return self.repo.default_signature
+        except KeyError as exc:
+            raise SCMError(
+                "Git username and email must be configured"
+            ) from exc
+
     @staticmethod
     def clone(
         url: str,
@@ -328,7 +337,7 @@ class Pygit2Backend(BaseGitBackend):  # pylint:disable=abstract-method
         from dvc.scm.git import Stash
 
         oid = self.repo.stash(
-            self.repo.default_signature,
+            self.default_signature,
             message=message,
             include_untracked=include_untracked,
         )
@@ -503,7 +512,7 @@ class Pygit2Backend(BaseGitBackend):  # pylint:disable=abstract-method
             raise MergeConflictError("Merge contained conflicts")
 
         if commit:
-            user = self.repo.default_signature
+            user = self.default_signature
             tree = self.repo.index.write_tree()
             merge_commit = self.repo.create_commit(
                 "HEAD", user, user, msg, tree, [self.repo.head.target, rev]