Repository: jelmer/dulwich

Issue:
includeIf hasconfig breaks config file parsing.
Given:

```
[includeIf  "hasconfig:remote.*.url:ssh://org-*@github.com/**"]
     path = ~/.config/git/.work
```

Dulwich fails to handle this in git config:

```
../build/lipy-scm/environments/development-venv/lib/python3.10/site-packages/dulwich/repo.py:1681: in _init_maybe_bare
    config = StackedConfig.default()
../build/lipy-scm/environments/development-venv/lib/python3.10/site-packages/dulwich/config.py:701: in default
    return cls(cls.default_backends())
../build/lipy-scm/environments/development-venv/lib/python3.10/site-packages/dulwich/config.py:721: in default_backends
    cf = ConfigFile.from_path(path)
../build/lipy-scm/environments/development-venv/lib/python3.10/site-packages/dulwich/config.py:596: in from_path
    ret = cls.from_file(f)
../build/lipy-scm/environments/development-venv/lib/python3.10/site-packages/dulwich/config.py:556: in from_file
    section, line = _parse_section_header_line(line)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

line = b''

    def _parse_section_header_line(line: bytes) -> Tuple[Section, bytes]:
        # Parse section header ("[bla]")
        line = _strip_comments(line).rstrip()
        in_quotes = False
        escaped = False
        for i, c in enumerate(line):
            if escaped:
                escaped = False
                continue
            if c == ord(b'"'):
                in_quotes = not in_quotes
            if c == ord(b'\\'):
                escaped = True
            if c == ord(b']') and not in_quotes:
                last = i
                break
        else:
            raise ValueError("expected trailing ]")
        pts = line[1:last].split(b" ", 1)
        line = line[last + 1:]
        section: Section
        if len(pts) == 2:
            if pts[1][:1] != b'"' or pts[1][-1:] != b'"':
>               raise ValueError("Invalid subsection %r" % pts[1])
E               ValueError: Invalid subsection b' "hasconfig:remote.*.url:ssh://org-*@github.com/**"'

../build/lipy-scm/environments/development-venv/lib/python3.10/site-packages/dulwich/config.py:513: ValueError
```

Hints from issue comments:

Solution patch:
diff --git a/dulwich/config.py b/dulwich/config.py
index e0163921..c0bb823c 100644
--- a/dulwich/config.py
+++ b/dulwich/config.py
@@ -25,13 +25,16 @@ Todo:
  * preserve formatting when updating configuration files
 """
 
+import logging
 import os
 import sys
 from collections.abc import Iterable, Iterator, KeysView, MutableMapping
 from contextlib import suppress
+from pathlib import Path
 from typing import (
     Any,
     BinaryIO,
+    Callable,
     Optional,
     Union,
     overload,
@@ -39,9 +42,72 @@ from typing import (
 
 from .file import GitFile
 
+logger = logging.getLogger(__name__)
+
+# Type for file opener callback
+FileOpener = Callable[[Union[str, os.PathLike]], BinaryIO]
+
+# Security limits for include files
+MAX_INCLUDE_FILE_SIZE = 1024 * 1024  # 1MB max for included config files
+DEFAULT_MAX_INCLUDE_DEPTH = 10  # Maximum recursion depth for includes
+
 SENTINEL = object()
 
 
+def _match_gitdir_pattern(
+    path: bytes, pattern: bytes, ignorecase: bool = False
+) -> bool:
+    """Simple gitdir pattern matching for includeIf conditions.
+
+    This handles the basic gitdir patterns used in includeIf directives.
+    """
+    # Convert to strings for easier manipulation
+    path_str = path.decode("utf-8", errors="replace")
+    pattern_str = pattern.decode("utf-8", errors="replace")
+
+    # Normalize paths to use forward slashes for consistent matching
+    path_str = path_str.replace("\\", "/")
+    pattern_str = pattern_str.replace("\\", "/")
+
+    if ignorecase:
+        path_str = path_str.lower()
+        pattern_str = pattern_str.lower()
+
+    # Handle the common cases for gitdir patterns
+    if pattern_str.startswith("**/") and pattern_str.endswith("/**"):
+        # Pattern like **/dirname/** should match any path containing dirname
+        dirname = pattern_str[3:-3]  # Remove **/ and /**
+        # Check if path contains the directory name as a path component
+        return ("/" + dirname + "/") in path_str or path_str.endswith("/" + dirname)
+    elif pattern_str.startswith("**/"):
+        # Pattern like **/filename
+        suffix = pattern_str[3:]  # Remove **/
+        return suffix in path_str or path_str.endswith("/" + suffix)
+    elif pattern_str.endswith("/**"):
+        # Pattern like /path/to/dir/** should match /path/to/dir and any subdirectory
+        base_pattern = pattern_str[:-3]  # Remove /**
+        return path_str == base_pattern or path_str.startswith(base_pattern + "/")
+    elif "**" in pattern_str:
+        # Handle patterns with ** in the middle
+        parts = pattern_str.split("**")
+        if len(parts) == 2:
+            prefix, suffix = parts
+            # Path must start with prefix and end with suffix (if any)
+            if prefix and not path_str.startswith(prefix):
+                return False
+            if suffix and not path_str.endswith(suffix):
+                return False
+            return True
+
+    # Direct match or simple glob pattern
+    if "*" in pattern_str or "?" in pattern_str or "[" in pattern_str:
+        import fnmatch
+
+        return fnmatch.fnmatch(path_str, pattern_str)
+    else:
+        return path_str == pattern_str
+
+
 def lower_key(key):
     if isinstance(key, (bytes, str)):
         return key.lower()
@@ -50,7 +116,7 @@ def lower_key(key):
         # For config sections, only lowercase the section name (first element)
         # but preserve the case of subsection names (remaining elements)
         if len(key) > 0:
-            return (key[0].lower(),) + key[1:]
+            return (key[0].lower(), *key[1:])
         return key
 
     return key
@@ -559,10 +625,19 @@ def _parse_section_header_line(line: bytes) -> tuple[Section, bytes]:
     line = line[last + 1 :]
     section: Section
     if len(pts) == 2:
-        if pts[1][:1] != b'"' or pts[1][-1:] != b'"':
-            raise ValueError(f"Invalid subsection {pts[1]!r}")
-        else:
+        # Handle subsections - Git allows more complex syntax for certain sections like includeIf
+        if pts[1][:1] == b'"' and pts[1][-1:] == b'"':
+            # Standard quoted subsection
             pts[1] = pts[1][1:-1]
+        elif pts[0] == b"includeIf":
+            # Special handling for includeIf sections which can have complex conditions
+            # Git allows these without strict quote validation
+            pts[1] = pts[1].strip()
+            if pts[1][:1] == b'"' and pts[1][-1:] == b'"':
+                pts[1] = pts[1][1:-1]
+        else:
+            # Other sections must have quoted subsections
+            raise ValueError(f"Invalid subsection {pts[1]!r}")
         if not _check_section_name(pts[0]):
             raise ValueError(f"invalid section name {pts[0]!r}")
         section = (pts[0], pts[1])
@@ -589,11 +664,39 @@ class ConfigFile(ConfigDict):
     ) -> None:
         super().__init__(values=values, encoding=encoding)
         self.path: Optional[str] = None
+        self._included_paths: set[str] = set()  # Track included files to prevent cycles
 
     @classmethod
-    def from_file(cls, f: BinaryIO) -> "ConfigFile":
-        """Read configuration from a file-like object."""
+    def from_file(
+        cls,
+        f: BinaryIO,
+        *,
+        config_dir: Optional[str] = None,
+        repo_dir: Optional[str] = None,
+        included_paths: Optional[set[str]] = None,
+        include_depth: int = 0,
+        max_include_depth: int = DEFAULT_MAX_INCLUDE_DEPTH,
+        file_opener: Optional[FileOpener] = None,
+    ) -> "ConfigFile":
+        """Read configuration from a file-like object.
+
+        Args:
+            f: File-like object to read from
+            config_dir: Directory containing the config file (for relative includes)
+            repo_dir: Repository directory (for gitdir conditions)
+            included_paths: Set of already included paths (to prevent cycles)
+            include_depth: Current include depth (to prevent infinite recursion)
+            max_include_depth: Maximum allowed include depth
+            file_opener: Optional callback to open included files
+        """
+        if include_depth > max_include_depth:
+            # Prevent excessive recursion
+            raise ValueError(f"Maximum include depth ({max_include_depth}) exceeded")
+
         ret = cls()
+        if included_paths is not None:
+            ret._included_paths = included_paths.copy()
+
         section: Optional[Section] = None
         setting = None
         continuation = None
@@ -626,6 +729,19 @@ class ConfigFile(ConfigDict):
                     continuation = None
                     value = _parse_string(value)
                     ret._values[section][setting] = value
+
+                    # Process include/includeIf directives
+                    ret._handle_include_directive(
+                        section,
+                        setting,
+                        value,
+                        config_dir=config_dir,
+                        repo_dir=repo_dir,
+                        include_depth=include_depth,
+                        max_include_depth=max_include_depth,
+                        file_opener=file_opener,
+                    )
+
                     setting = None
             else:  # continuation line
                 assert continuation is not None
@@ -638,16 +754,247 @@ class ConfigFile(ConfigDict):
                     continuation += line
                     value = _parse_string(continuation)
                     ret._values[section][setting] = value
+
+                    # Process include/includeIf directives
+                    ret._handle_include_directive(
+                        section,
+                        setting,
+                        value,
+                        config_dir=config_dir,
+                        repo_dir=repo_dir,
+                        include_depth=include_depth,
+                        max_include_depth=max_include_depth,
+                        file_opener=file_opener,
+                    )
+
                     continuation = None
                     setting = None
         return ret
 
+    def _handle_include_directive(
+        self,
+        section: Optional[Section],
+        setting: bytes,
+        value: bytes,
+        *,
+        config_dir: Optional[str],
+        repo_dir: Optional[str],
+        include_depth: int,
+        max_include_depth: int,
+        file_opener: Optional[FileOpener],
+    ) -> None:
+        """Handle include/includeIf directives during config parsing."""
+        if (
+            section is not None
+            and setting == b"path"
+            and (
+                section[0].lower() == b"include"
+                or (len(section) > 1 and section[0].lower() == b"includeif")
+            )
+        ):
+            self._process_include(
+                section,
+                value,
+                config_dir=config_dir,
+                repo_dir=repo_dir,
+                include_depth=include_depth,
+                max_include_depth=max_include_depth,
+                file_opener=file_opener,
+            )
+
+    def _process_include(
+        self,
+        section: Section,
+        path_value: bytes,
+        *,
+        config_dir: Optional[str],
+        repo_dir: Optional[str],
+        include_depth: int,
+        max_include_depth: int,
+        file_opener: Optional[FileOpener],
+    ) -> None:
+        """Process an include or includeIf directive."""
+        path_str = path_value.decode(self.encoding, errors="replace")
+
+        # Handle includeIf conditions
+        if len(section) > 1 and section[0].lower() == b"includeif":
+            condition = section[1].decode(self.encoding, errors="replace")
+            if not self._evaluate_includeif_condition(condition, repo_dir):
+                return
+
+        # Resolve the include path
+        include_path = self._resolve_include_path(path_str, config_dir)
+        if not include_path:
+            return
+
+        # Check for circular includes
+        try:
+            abs_path = str(Path(include_path).resolve())
+        except (OSError, ValueError) as e:
+            # Invalid path - log and skip
+            logger.debug("Invalid include path %r: %s", include_path, e)
+            return
+        if abs_path in self._included_paths:
+            return
+
+        # Load and merge the included file
+        try:
+            # Use provided file opener or default to GitFile
+            if file_opener is None:
+
+                def opener(path):
+                    return GitFile(path, "rb")
+            else:
+                opener = file_opener
+
+            with opener(include_path) as included_file:
+                # Track this path to prevent cycles
+                self._included_paths.add(abs_path)
+
+                # Parse the included file
+                included_config = ConfigFile.from_file(
+                    included_file,
+                    config_dir=os.path.dirname(include_path),
+                    repo_dir=repo_dir,
+                    included_paths=self._included_paths,
+                    include_depth=include_depth + 1,
+                    max_include_depth=max_include_depth,
+                    file_opener=file_opener,
+                )
+
+                # Merge the included configuration
+                self._merge_config(included_config)
+        except OSError as e:
+            # Git silently ignores missing or unreadable include files
+            # Log for debugging purposes
+            logger.debug("Failed to read include file %r: %s", include_path, e)
+
+    def _merge_config(self, other: "ConfigFile") -> None:
+        """Merge another config file into this one."""
+        for section, values in other._values.items():
+            if section not in self._values:
+                self._values[section] = CaseInsensitiveOrderedMultiDict()
+            for key, value in values.items():
+                self._values[section][key] = value
+
+    def _resolve_include_path(
+        self, path: str, config_dir: Optional[str]
+    ) -> Optional[str]:
+        """Resolve an include path to an absolute path."""
+        # Expand ~ to home directory
+        path = os.path.expanduser(path)
+
+        # If path is relative and we have a config directory, make it relative to that
+        if not os.path.isabs(path) and config_dir:
+            path = os.path.join(config_dir, path)
+
+        return path
+
+    def _evaluate_includeif_condition(
+        self, condition: str, repo_dir: Optional[str]
+    ) -> bool:
+        """Evaluate an includeIf condition."""
+        if condition.startswith("gitdir:"):
+            return self._evaluate_gitdir_condition(condition[7:], repo_dir)
+        elif condition.startswith("gitdir/i:"):
+            return self._evaluate_gitdir_condition(
+                condition[9:], repo_dir, case_sensitive=False
+            )
+        elif condition.startswith("hasconfig:"):
+            # hasconfig conditions require special handling and access to the full config
+            # For now, we'll skip these as they require more complex implementation
+            return False
+        else:
+            # Unknown condition type - log and ignore (Git behavior)
+            logger.debug("Unknown includeIf condition: %r", condition)
+            return False
+
+    def _evaluate_gitdir_condition(
+        self, pattern: str, repo_dir: Optional[str], case_sensitive: bool = True
+    ) -> bool:
+        """Evaluate a gitdir condition using simplified pattern matching."""
+        if not repo_dir:
+            return False
+
+        # Skip relative patterns for now (would need config file path)
+        if pattern.startswith("./"):
+            return False
+
+        # Normalize repository path
+        try:
+            repo_path = str(Path(repo_dir).resolve())
+        except (OSError, ValueError) as e:
+            logger.debug("Invalid repository path %r: %s", repo_dir, e)
+            return False
+
+        # Expand ~ in pattern and normalize
+        pattern = os.path.expanduser(pattern)
+        pattern = self._normalize_gitdir_pattern(pattern)
+
+        # Use simple pattern matching for gitdir conditions
+        pattern_bytes = pattern.encode("utf-8", errors="replace")
+        repo_path_bytes = repo_path.encode("utf-8", errors="replace")
+
+        return _match_gitdir_pattern(
+            repo_path_bytes, pattern_bytes, ignorecase=not case_sensitive
+        )
+
+    def _normalize_gitdir_pattern(self, pattern: str) -> str:
+        """Normalize a gitdir pattern following Git's rules."""
+        # Normalize path separators to forward slashes
+        pattern = pattern.replace("\\", "/")
+
+        # If pattern doesn't start with ~/, ./, /, drive letter (Windows), or **, prepend **/
+        if not pattern.startswith(("~/", "./", "/", "**")):
+            # Check for Windows absolute path (e.g., C:/, D:/)
+            if len(pattern) >= 2 and pattern[1] == ":":
+                pass  # Don't prepend **/ for Windows absolute paths
+            else:
+                pattern = "**/" + pattern
+
+        # If pattern ends with /, append **
+        if pattern.endswith("/"):
+            pattern = pattern + "**"
+
+        return pattern
+
     @classmethod
-    def from_path(cls, path: Union[str, os.PathLike]) -> "ConfigFile":
-        """Read configuration from a file on disk."""
-        with GitFile(path, "rb") as f:
-            ret = cls.from_file(f)
-            ret.path = os.fspath(path)
+    def from_path(
+        cls,
+        path: Union[str, os.PathLike],
+        *,
+        repo_dir: Optional[str] = None,
+        max_include_depth: int = DEFAULT_MAX_INCLUDE_DEPTH,
+        file_opener: Optional[FileOpener] = None,
+    ) -> "ConfigFile":
+        """Read configuration from a file on disk.
+
+        Args:
+            path: Path to the configuration file
+            repo_dir: Repository directory (for gitdir conditions in includeIf)
+            max_include_depth: Maximum allowed include depth
+            file_opener: Optional callback to open included files
+        """
+        abs_path = os.fspath(path)
+        config_dir = os.path.dirname(abs_path)
+
+        # Use provided file opener or default to GitFile
+        if file_opener is None:
+
+            def opener(p):
+                return GitFile(p, "rb")
+        else:
+            opener = file_opener
+
+        with opener(abs_path) as f:
+            ret = cls.from_file(
+                f,
+                config_dir=config_dir,
+                repo_dir=repo_dir,
+                max_include_depth=max_include_depth,
+                file_opener=file_opener,
+            )
+            ret.path = abs_path
             return ret
 
     def write_to_path(self, path: Optional[Union[str, os.PathLike]] = None) -> None:
diff --git a/dulwich/repo.py b/dulwich/repo.py
index f9f5d941..ba1fb690 100644
--- a/dulwich/repo.py
+++ b/dulwich/repo.py
@@ -1727,7 +1727,8 @@ class Repo(BaseRepo):
 
         path = os.path.join(self.commondir(), "config.worktree")
         try:
-            return ConfigFile.from_path(path)
+            # Pass the git directory (not working tree) for includeIf gitdir conditions
+            return ConfigFile.from_path(path, repo_dir=self._controldir)
         except FileNotFoundError:
             cf = ConfigFile()
             cf.path = path
@@ -1742,7 +1743,8 @@ class Repo(BaseRepo):
 
         path = os.path.join(self._commondir, "config")
         try:
-            return ConfigFile.from_path(path)
+            # Pass the git directory (not working tree) for includeIf gitdir conditions
+            return ConfigFile.from_path(path, repo_dir=self._controldir)
         except FileNotFoundError:
             ret = ConfigFile()
             ret.path = path


Test patch:
diff --git a/tests/test_config.py b/tests/test_config.py
index 694ef434..27c0afcf 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -23,6 +23,7 @@
 
 import os
 import sys
+import tempfile
 from io import BytesIO
 from unittest import skipIf
 from unittest.mock import patch
@@ -167,6 +168,21 @@ class ConfigFileTests(TestCase):
         cf = self.from_file(b"[branch.foo]\nfoo = bar\n")
         self.assertEqual(b"bar", cf.get((b"branch", b"foo"), b"foo"))
 
+    def test_from_file_includeif_hasconfig(self) -> None:
+        """Test parsing includeIf sections with hasconfig conditions."""
+        # Test case from issue #1216
+        cf = self.from_file(
+            b'[includeIf "hasconfig:remote.*.url:ssh://org-*@github.com/**"]\n'
+            b"    path = ~/.config/git/.work\n"
+        )
+        self.assertEqual(
+            b"~/.config/git/.work",
+            cf.get(
+                (b"includeIf", b"hasconfig:remote.*.url:ssh://org-*@github.com/**"),
+                b"path",
+            ),
+        )
+
     def test_write_preserve_multivar(self) -> None:
         cf = self.from_file(b"[core]\nfoo = bar\nfoo = blah\n")
         f = BytesIO()
@@ -357,6 +373,430 @@ who\"
             # Clean up
             os.unlink(temp_path)
 
+    def test_include_basic(self) -> None:
+        """Test basic include functionality."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Create included config file
+            included_path = os.path.join(tmpdir, "included.config")
+            with open(included_path, "wb") as f:
+                f.write(
+                    b"[user]\n    name = Included User\n    email = included@example.com\n"
+                )
+
+            # Create main config with include
+            main_config = self.from_file(
+                b"[user]\n    name = Main User\n[include]\n    path = included.config\n"
+            )
+
+            # Should not include anything without proper directory context
+            self.assertEqual(b"Main User", main_config.get((b"user",), b"name"))
+            with self.assertRaises(KeyError):
+                main_config.get((b"user",), b"email")
+
+            # Now test with proper file loading
+            main_path = os.path.join(tmpdir, "main.config")
+            with open(main_path, "wb") as f:
+                f.write(
+                    b"[user]\n    name = Main User\n[include]\n    path = included.config\n"
+                )
+
+            # Load from path to get include functionality
+            cf = ConfigFile.from_path(main_path)
+            self.assertEqual(b"Included User", cf.get((b"user",), b"name"))
+            self.assertEqual(b"included@example.com", cf.get((b"user",), b"email"))
+
+    def test_include_absolute_path(self) -> None:
+        """Test include with absolute path."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Use realpath to resolve any symlinks (important on macOS and Windows)
+            tmpdir = os.path.realpath(tmpdir)
+
+            # Create included config file
+            included_path = os.path.join(tmpdir, "included.config")
+            with open(included_path, "wb") as f:
+                f.write(b"[core]\n    bare = true\n")
+
+            # Create main config with absolute include path
+            main_path = os.path.join(tmpdir, "main.config")
+            with open(main_path, "wb") as f:
+                # Properly escape backslashes in Windows paths
+                escaped_path = included_path.replace("\\", "\\\\")
+                f.write(f"[include]\n    path = {escaped_path}\n".encode())
+
+            cf = ConfigFile.from_path(main_path)
+            self.assertEqual(b"true", cf.get((b"core",), b"bare"))
+
+    def test_includeif_gitdir_match(self) -> None:
+        """Test includeIf with gitdir condition that matches."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            repo_dir = os.path.join(tmpdir, "myrepo")
+            os.makedirs(repo_dir)
+            # Use realpath to resolve any symlinks (important on macOS)
+            repo_dir = os.path.realpath(repo_dir)
+
+            # Create included config file
+            included_path = os.path.join(tmpdir, "work.config")
+            with open(included_path, "wb") as f:
+                f.write(b"[user]\n    email = work@example.com\n")
+
+            # Create main config with includeIf
+            main_path = os.path.join(tmpdir, "main.config")
+            with open(main_path, "wb") as f:
+                f.write(
+                    f'[includeIf "gitdir:{repo_dir}/"]\n    path = work.config\n'.encode()
+                )
+
+            # Load with matching repo_dir
+            cf = ConfigFile.from_path(main_path, repo_dir=repo_dir)
+            self.assertEqual(b"work@example.com", cf.get((b"user",), b"email"))
+
+    def test_includeif_gitdir_no_match(self) -> None:
+        """Test includeIf with gitdir condition that doesn't match."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            repo_dir = os.path.join(tmpdir, "myrepo")
+            other_dir = os.path.join(tmpdir, "other")
+            os.makedirs(repo_dir)
+            os.makedirs(other_dir)
+            # Use realpath to resolve any symlinks (important on macOS)
+            repo_dir = os.path.realpath(repo_dir)
+            other_dir = os.path.realpath(other_dir)
+
+            # Create included config file
+            included_path = os.path.join(tmpdir, "work.config")
+            with open(included_path, "wb") as f:
+                f.write(b"[user]\n    email = work@example.com\n")
+
+            # Create main config with includeIf
+            main_path = os.path.join(tmpdir, "main.config")
+            with open(main_path, "wb") as f:
+                f.write(
+                    f'[includeIf "gitdir:{repo_dir}/"]\n    path = work.config\n'.encode()
+                )
+
+            # Load with non-matching repo_dir
+            cf = ConfigFile.from_path(main_path, repo_dir=other_dir)
+            with self.assertRaises(KeyError):
+                cf.get((b"user",), b"email")
+
+    def test_includeif_gitdir_pattern(self) -> None:
+        """Test includeIf with gitdir pattern matching."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Use realpath to resolve any symlinks
+            tmpdir = os.path.realpath(tmpdir)
+            work_dir = os.path.join(tmpdir, "work", "project1")
+            os.makedirs(work_dir)
+
+            # Create included config file
+            included_path = os.path.join(tmpdir, "work.config")
+            with open(included_path, "wb") as f:
+                f.write(b"[user]\n    email = work@company.com\n")
+
+            # Create main config with pattern
+            main_path = os.path.join(tmpdir, "main.config")
+            with open(main_path, "wb") as f:
+                # Pattern that should match any repo under work/
+                f.write(b'[includeIf "gitdir:work/**"]\n    path = work.config\n')
+
+            # Load with matching pattern
+            cf = ConfigFile.from_path(main_path, repo_dir=work_dir)
+            self.assertEqual(b"work@company.com", cf.get((b"user",), b"email"))
+
+    def test_include_circular(self) -> None:
+        """Test that circular includes are handled properly."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Create two configs that include each other
+            config1_path = os.path.join(tmpdir, "config1")
+            config2_path = os.path.join(tmpdir, "config2")
+
+            with open(config1_path, "wb") as f:
+                f.write(b"[user]\n    name = User1\n[include]\n    path = config2\n")
+
+            with open(config2_path, "wb") as f:
+                f.write(
+                    b"[user]\n    email = user2@example.com\n[include]\n    path = config1\n"
+                )
+
+            # Should handle circular includes gracefully
+            cf = ConfigFile.from_path(config1_path)
+            self.assertEqual(b"User1", cf.get((b"user",), b"name"))
+            self.assertEqual(b"user2@example.com", cf.get((b"user",), b"email"))
+
+    def test_include_missing_file(self) -> None:
+        """Test that missing include files are ignored."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Create config with include of non-existent file
+            config_path = os.path.join(tmpdir, "config")
+            with open(config_path, "wb") as f:
+                f.write(
+                    b"[user]\n    name = TestUser\n[include]\n    path = missing.config\n"
+                )
+
+            # Should not fail, just ignore missing include
+            cf = ConfigFile.from_path(config_path)
+            self.assertEqual(b"TestUser", cf.get((b"user",), b"name"))
+
+    def test_include_depth_limit(self) -> None:
+        """Test that excessive include depth is prevented."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Create a chain of includes that exceeds depth limit
+            for i in range(15):
+                config_path = os.path.join(tmpdir, f"config{i}")
+                with open(config_path, "wb") as f:
+                    if i == 0:
+                        f.write(b"[user]\n    name = User0\n")
+                    f.write(f"[include]\n    path = config{i + 1}\n".encode())
+
+            # Should raise error due to depth limit
+            with self.assertRaises(ValueError) as cm:
+                ConfigFile.from_path(os.path.join(tmpdir, "config0"))
+            self.assertIn("include depth", str(cm.exception))
+
+    def test_include_with_custom_file_opener(self) -> None:
+        """Test include functionality with a custom file opener for security."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Create config files
+            included_path = os.path.join(tmpdir, "included.config")
+            with open(included_path, "wb") as f:
+                f.write(b"[user]\n    email = custom@example.com\n")
+
+            restricted_path = os.path.join(tmpdir, "restricted.config")
+            with open(restricted_path, "wb") as f:
+                f.write(b"[user]\n    email = restricted@example.com\n")
+
+            main_path = os.path.join(tmpdir, "main.config")
+            with open(main_path, "wb") as f:
+                f.write(b"[user]\n    name = Test User\n")
+                f.write(b"[include]\n    path = included.config\n")
+                f.write(b"[include]\n    path = restricted.config\n")
+
+            # Define a custom file opener that restricts access
+            allowed_files = {included_path, main_path}
+
+            def secure_file_opener(path):
+                path_str = os.fspath(path)
+                if path_str not in allowed_files:
+                    raise PermissionError(f"Access denied to {path}")
+                return open(path_str, "rb")
+
+            # Load config with restricted file access
+            cf = ConfigFile.from_path(main_path, file_opener=secure_file_opener)
+
+            # Should have the main config and included config, but not restricted
+            self.assertEqual(b"Test User", cf.get((b"user",), b"name"))
+            self.assertEqual(b"custom@example.com", cf.get((b"user",), b"email"))
+            # Email from restricted.config should not be loaded
+
+    def test_unknown_includeif_condition(self) -> None:
+        """Test that unknown includeIf conditions are silently ignored (like Git)."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Create included config file
+            included_path = os.path.join(tmpdir, "included.config")
+            with open(included_path, "wb") as f:
+                f.write(b"[user]\n    email = included@example.com\n")
+
+            # Create main config with unknown includeIf condition
+            main_path = os.path.join(tmpdir, "main.config")
+            with open(main_path, "wb") as f:
+                f.write(b"[user]\n    name = Main User\n")
+                f.write(
+                    b'[includeIf "unknowncondition:foo"]\n    path = included.config\n'
+                )
+
+            # Should not fail, just ignore the unknown condition
+            cf = ConfigFile.from_path(main_path)
+            self.assertEqual(b"Main User", cf.get((b"user",), b"name"))
+            # Email should not be included because condition is unknown
+            with self.assertRaises(KeyError):
+                cf.get((b"user",), b"email")
+
+    def test_missing_include_file_logging(self) -> None:
+        """Test that missing include files are logged but don't cause failure."""
+        import logging
+        from io import StringIO
+
+        # Set up logging capture
+        log_capture = StringIO()
+        handler = logging.StreamHandler(log_capture)
+        handler.setLevel(logging.DEBUG)
+        logger = logging.getLogger("dulwich.config")
+        logger.addHandler(handler)
+        logger.setLevel(logging.DEBUG)
+
+        try:
+            with tempfile.TemporaryDirectory() as tmpdir:
+                config_path = os.path.join(tmpdir, "test.config")
+                with open(config_path, "wb") as f:
+                    f.write(b"[user]\n    name = Test User\n")
+                    f.write(b"[include]\n    path = nonexistent.config\n")
+
+                # Should not fail, just log
+                cf = ConfigFile.from_path(config_path)
+                self.assertEqual(b"Test User", cf.get((b"user",), b"name"))
+
+                # Check that it was logged
+                log_output = log_capture.getvalue()
+                self.assertIn("Failed to read include file", log_output)
+                self.assertIn("nonexistent.config", log_output)
+        finally:
+            logger.removeHandler(handler)
+
+    def test_invalid_include_path_logging(self) -> None:
+        """Test that invalid include paths are logged but don't cause failure."""
+        import logging
+        from io import StringIO
+
+        # Set up logging capture
+        log_capture = StringIO()
+        handler = logging.StreamHandler(log_capture)
+        handler.setLevel(logging.DEBUG)
+        logger = logging.getLogger("dulwich.config")
+        logger.addHandler(handler)
+        logger.setLevel(logging.DEBUG)
+
+        try:
+            with tempfile.TemporaryDirectory() as tmpdir:
+                config_path = os.path.join(tmpdir, "test.config")
+                with open(config_path, "wb") as f:
+                    f.write(b"[user]\n    name = Test User\n")
+                    # Use null bytes which are invalid in paths
+                    f.write(b"[include]\n    path = /invalid\x00path/file.config\n")
+
+                # Should not fail, just log
+                cf = ConfigFile.from_path(config_path)
+                self.assertEqual(b"Test User", cf.get((b"user",), b"name"))
+
+                # Check that it was logged
+                log_output = log_capture.getvalue()
+                self.assertIn("Invalid include path", log_output)
+        finally:
+            logger.removeHandler(handler)
+
+    def test_unknown_includeif_condition_logging(self) -> None:
+        """Test that unknown includeIf conditions are logged."""
+        import logging
+        from io import StringIO
+
+        # Set up logging capture
+        log_capture = StringIO()
+        handler = logging.StreamHandler(log_capture)
+        handler.setLevel(logging.DEBUG)
+        logger = logging.getLogger("dulwich.config")
+        logger.addHandler(handler)
+        logger.setLevel(logging.DEBUG)
+
+        try:
+            with tempfile.TemporaryDirectory() as tmpdir:
+                config_path = os.path.join(tmpdir, "test.config")
+                with open(config_path, "wb") as f:
+                    f.write(b"[user]\n    name = Test User\n")
+                    f.write(
+                        b'[includeIf "futurefeature:value"]\n    path = other.config\n'
+                    )
+
+                # Should not fail, just log
+                cf = ConfigFile.from_path(config_path)
+                self.assertEqual(b"Test User", cf.get((b"user",), b"name"))
+
+                # Check that it was logged
+                log_output = log_capture.getvalue()
+                self.assertIn("Unknown includeIf condition", log_output)
+                self.assertIn("futurefeature:value", log_output)
+        finally:
+            logger.removeHandler(handler)
+
+    def test_includeif_with_custom_file_opener(self) -> None:
+        """Test includeIf functionality with custom file opener."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Use realpath to resolve any symlinks
+            tmpdir = os.path.realpath(tmpdir)
+            repo_dir = os.path.join(tmpdir, "work", "project", ".git")
+            os.makedirs(repo_dir, exist_ok=True)
+
+            # Create config files
+            work_config_path = os.path.join(tmpdir, "work.config")
+            with open(work_config_path, "wb") as f:
+                f.write(b"[user]\n    email = work@company.com\n")
+
+            personal_config_path = os.path.join(tmpdir, "personal.config")
+            with open(personal_config_path, "wb") as f:
+                f.write(b"[user]\n    email = personal@home.com\n")
+
+            main_path = os.path.join(tmpdir, "main.config")
+            with open(main_path, "wb") as f:
+                f.write(b"[user]\n    name = Test User\n")
+                f.write(b'[includeIf "gitdir:**/work/**"]\n')
+                escaped_work_path = work_config_path.replace("\\", "\\\\")
+                f.write(f"    path = {escaped_work_path}\n".encode())
+                f.write(b'[includeIf "gitdir:**/personal/**"]\n')
+                escaped_personal_path = personal_config_path.replace("\\", "\\\\")
+                f.write(f"    path = {escaped_personal_path}\n".encode())
+
+            # Track which files were opened
+            opened_files = []
+
+            def tracking_file_opener(path):
+                path_str = os.fspath(path)
+                opened_files.append(path_str)
+                return open(path_str, "rb")
+
+            # Load config with tracking file opener
+            cf = ConfigFile.from_path(
+                main_path, repo_dir=repo_dir, file_opener=tracking_file_opener
+            )
+
+            # Check results
+            self.assertEqual(b"Test User", cf.get((b"user",), b"name"))
+            self.assertEqual(b"work@company.com", cf.get((b"user",), b"email"))
+
+            # Verify that only the matching includeIf file was opened
+            self.assertIn(main_path, opened_files)
+            self.assertIn(work_config_path, opened_files)
+            self.assertNotIn(personal_config_path, opened_files)
+
+    def test_custom_file_opener_with_include_depth(self) -> None:
+        """Test that custom file opener is passed through include chain."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Use realpath to resolve any symlinks
+            tmpdir = os.path.realpath(tmpdir)
+
+            # Create a chain of includes
+            final_config = os.path.join(tmpdir, "final.config")
+            with open(final_config, "wb") as f:
+                f.write(b"[feature]\n    enabled = true\n")
+
+            middle_config = os.path.join(tmpdir, "middle.config")
+            with open(middle_config, "wb") as f:
+                f.write(b"[user]\n    email = test@example.com\n")
+                escaped_final_config = final_config.replace("\\", "\\\\")
+                f.write(f"[include]\n    path = {escaped_final_config}\n".encode())
+
+            main_config = os.path.join(tmpdir, "main.config")
+            with open(main_config, "wb") as f:
+                f.write(b"[user]\n    name = Test User\n")
+                escaped_middle_config = middle_config.replace("\\", "\\\\")
+                f.write(f"[include]\n    path = {escaped_middle_config}\n".encode())
+
+            # Track file access order
+            access_order = []
+
+            def ordering_file_opener(path):
+                path_str = os.fspath(path)
+                access_order.append(os.path.basename(path_str))
+                return open(path_str, "rb")
+
+            # Load config
+            cf = ConfigFile.from_path(main_config, file_opener=ordering_file_opener)
+
+            # Verify all values were loaded
+            self.assertEqual(b"Test User", cf.get((b"user",), b"name"))
+            self.assertEqual(b"test@example.com", cf.get((b"user",), b"email"))
+            self.assertEqual(b"true", cf.get((b"feature",), b"enabled"))
+
+            # Verify access order
+            self.assertEqual(
+                ["main.config", "middle.config", "final.config"], access_order
+            )
+
 
 class ConfigDictTests(TestCase):
     def test_get_set(self) -> None:
diff --git a/tests/test_repository.py b/tests/test_repository.py
index 3ed2c07a..ce1d07f2 100644
--- a/tests/test_repository.py
+++ b/tests/test_repository.py
@@ -1697,3 +1697,143 @@ class CheckUserIdentityTests(TestCase):
         self.assertRaises(
             InvalidUserIdentity, check_user_identity, b"Contains\nnewline byte <>"
         )
+
+
+class RepoConfigIncludeIfTests(TestCase):
+    """Test includeIf functionality in repository config loading."""
+
+    def test_repo_config_includeif_gitdir(self) -> None:
+        """Test that includeIf gitdir conditions work when loading repo config."""
+        import tempfile
+
+        from dulwich.repo import Repo
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Create a repository
+            repo_path = os.path.join(tmpdir, "myrepo")
+            r = Repo.init(repo_path, mkdir=True)
+            # Use realpath to resolve any symlinks (important on macOS)
+            repo_path = os.path.realpath(repo_path)
+
+            # Create an included config file
+            included_path = os.path.join(tmpdir, "work.config")
+            with open(included_path, "wb") as f:
+                f.write(b"[user]\n    email = work@example.com\n")
+
+            # Add includeIf to the repo config
+            config_path = os.path.join(repo_path, ".git", "config")
+            with open(config_path, "ab") as f:
+                f.write(f'\n[includeIf "gitdir:{repo_path}/.git/"]\n'.encode())
+                escaped_path = included_path.replace("\\", "\\\\")
+                f.write(f"    path = {escaped_path}\n".encode())
+
+            # Close and reopen to reload config
+            r.close()
+            r = Repo(repo_path)
+
+            # Check if include was processed
+            config = r.get_config()
+            self.assertEqual(b"work@example.com", config.get((b"user",), b"email"))
+            r.close()
+
+    def test_repo_config_includeif_gitdir_pattern(self) -> None:
+        """Test includeIf gitdir pattern matching in repository config."""
+        import tempfile
+
+        from dulwich.repo import Repo
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Create a repository under "work" directory
+            work_dir = os.path.join(tmpdir, "work", "project1")
+            os.makedirs(os.path.dirname(work_dir), exist_ok=True)
+            r = Repo.init(work_dir, mkdir=True)
+
+            # Create an included config file
+            included_path = os.path.join(tmpdir, "work.config")
+            with open(included_path, "wb") as f:
+                f.write(b"[user]\n    email = work@company.com\n")
+
+            # Add includeIf with pattern to the repo config
+            config_path = os.path.join(work_dir, ".git", "config")
+            with open(config_path, "ab") as f:
+                # Use a pattern that will match paths containing /work/
+                f.write(b'\n[includeIf "gitdir:**/work/**"]\n')
+                escaped_path = included_path.replace("\\", "\\\\")
+                f.write(f"    path = {escaped_path}\n".encode())
+
+            # Close and reopen to reload config
+            r.close()
+            r = Repo(work_dir)
+
+            # Check if include was processed
+            config = r.get_config()
+            self.assertEqual(b"work@company.com", config.get((b"user",), b"email"))
+            r.close()
+
+    def test_repo_config_includeif_no_match(self) -> None:
+        """Test that includeIf doesn't include when condition doesn't match."""
+        import tempfile
+
+        from dulwich.repo import Repo
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Create a repository
+            repo_path = os.path.join(tmpdir, "personal", "project")
+            os.makedirs(os.path.dirname(repo_path), exist_ok=True)
+            r = Repo.init(repo_path, mkdir=True)
+
+            # Create an included config file
+            included_path = os.path.join(tmpdir, "work.config")
+            with open(included_path, "wb") as f:
+                f.write(b"[user]\n    email = work@company.com\n")
+
+            # Add includeIf that won't match
+            config_path = os.path.join(repo_path, ".git", "config")
+            with open(config_path, "ab") as f:
+                f.write(b'\n[includeIf "gitdir:**/work/**"]\n')
+                escaped_path = included_path.replace("\\", "\\\\")
+                f.write(f"    path = {escaped_path}\n".encode())
+
+            # Close and reopen to reload config
+            r.close()
+            r = Repo(repo_path)
+
+            # Check that include was NOT processed
+            config = r.get_config()
+            with self.assertRaises(KeyError):
+                config.get((b"user",), b"email")
+            r.close()
+
+    def test_bare_repo_config_includeif(self) -> None:
+        """Test includeIf in bare repository."""
+        import tempfile
+
+        from dulwich.repo import Repo
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Create a bare repository
+            repo_path = os.path.join(tmpdir, "bare.git")
+            r = Repo.init_bare(repo_path, mkdir=True)
+            # Use realpath to resolve any symlinks (important on macOS)
+            repo_path = os.path.realpath(repo_path)
+
+            # Create an included config file
+            included_path = os.path.join(tmpdir, "server.config")
+            with open(included_path, "wb") as f:
+                f.write(b"[receive]\n    denyNonFastForwards = true\n")
+
+            # Add includeIf to the repo config
+            config_path = os.path.join(repo_path, "config")
+            with open(config_path, "ab") as f:
+                f.write(f'\n[includeIf "gitdir:{repo_path}/"]\n'.encode())
+                escaped_path = included_path.replace("\\", "\\\\")
+                f.write(f"    path = {escaped_path}\n".encode())
+
+            # Close and reopen to reload config
+            r.close()
+            r = Repo(repo_path)
+
+            # Check if include was processed
+            config = r.get_config()
+            self.assertEqual(b"true", config.get((b"receive",), b"denyNonFastForwards"))
+            r.close()