add missing encoding conversion for diff contents

Author: muravvv

aider/repo.py

@@ -391,14 +391,20 @@ def get_diffs(self, fnames=None):
         try:
             if current_branch_has_commits:
                 args = ["HEAD", "--"] + list(fnames)
-                diffs += self.repo.git.diff(*args)
+                diffs += self.repo.git.diff(*args, stdout_as_string=False).decode(
+                    self.io.encoding, "replace"
+                )
                 return diffs
 
             wd_args = ["--"] + list(fnames)
             index_args = ["--cached"] + wd_args
 
-            diffs += self.repo.git.diff(*index_args)
-            diffs += self.repo.git.diff(*wd_args)
+            diffs += self.repo.git.diff(*index_args, stdout_as_string=False).decode(
+                self.io.encoding, "replace"
+            )
+            diffs += self.repo.git.diff(*wd_args, stdout_as_string=False).decode(
+                self.io.encoding, "replace"
+            )
 
             return diffs
         except ANY_GIT_ERROR as err:
@@ -412,7 +418,9 @@ def diff_commits(self, pretty, from_commit, to_commit):
             args += ["--color=never"]
 
         args += [from_commit, to_commit]
-        diffs = self.repo.git.diff(*args)
+        diffs = self.repo.git.diff(*args, stdout_as_string=False).decode(
+            self.io.encoding, "replace"
+        )
 
         return diffs
 

tests/basic/test_repo.py

@@ -59,6 +59,28 @@ def test_diffs_nonempty_repo(self):
             self.assertIn("index", diffs)
             self.assertIn("workingdir", diffs)
 
+    def test_diffs_with_single_byte_encoding(self):
+        with GitTemporaryDirectory():
+            encoding = "cp1251"
+
+            repo = git.Repo()
+
+            fname = Path("foo.txt")
+            fname.write_text("index\n", encoding=encoding)
+            repo.git.add(str(fname))
+
+            # Make a change with non-ASCII symbols in the working dir
+            fname.write_text("АБВ\n", encoding=encoding)
+
+            git_repo = GitRepo(InputOutput(encoding=encoding), None, ".")
+            diffs = git_repo.get_diffs()
+
+            # check that all diff output can be converted to utf-8 for sending to model
+            diffs.encode("utf-8")
+
+            self.assertIn("index", diffs)
+            self.assertIn("АБВ", diffs)
+
     def test_diffs_detached_head(self):
         with GitTemporaryDirectory():
             repo = git.Repo()