Patch file path in metadata not platform independent

Fixes #937

Author: spoorcc

CHANGELOG.rst

@@ -9,6 +9,7 @@ Release 0.12.0 (unreleased)
 * Allow multiple patches in manifest (#897)
 * Fallback and warn if patch is not UTF-8 encoded (#941)
 * Skip patches outside manifest dir (#0)
+* Make patch path in metadata platform independeny (#937)
 
 Release 0.11.0 (released 2026-01-03)
 ====================================

dfetch/manifest/project.py

@@ -226,7 +226,8 @@
 *DFetch* promotes upstreaming changes, but also allows local changes. These changes can be managed with local patch
 files. *DFetch* will apply the patch files in order every time a new upstream version is fetched. The patch file can
 be specified with the ``patch:`` attribute. This can be a single patch file or multiple. Patch files should be UTF-8
-encoded files.
+encoded files and using forward slashes is encouraged for cross-platform support. The path should be relative to the
+directory of the manifest.
 
 .. code-block:: yaml
 
@@ -241,11 +242,11 @@
         - name: cpputest
           vcs: git
           repo-path: cpputest/cpputest
-          patch: local_changes.patch
+          patch: patches/local_changes.patch
 
 The patch should be generated using the *Dfetch* :ref:`Diff` command.
-Alternately the patch can be generated manually as such.
-Note that the patch should be *relative* to the projects root.
+Alternately the patch can be generated manually as such and should be
+a *relative* patch, relative to the fetched projects root.
 
 .. tabs::
 

dfetch/project/subproject.py

@@ -5,6 +5,7 @@
 import pathlib
 from abc import ABC, abstractmethod
 from collections.abc import Sequence
+from pathlib import Path
 from typing import Optional
 
 from halo import Halo
@@ -141,24 +142,29 @@ def update(
 
     def _apply_patches(self) -> list[str]:
         """Apply the patches."""
-        manifest_dir = os.getcwd()
+        manifest_dir = Path(".").resolve()
         applied_patches = []
         for patch in self.__project.patch:
 
-            real_path = os.path.realpath(patch)
-            if os.path.commonprefix((real_path, manifest_dir)) != manifest_dir:
+            patch_path = (manifest_dir / patch).resolve()
+
+            try:
+                patch_path.relative_to(manifest_dir)
+            except ValueError:
                 self._log_project(
                     f'Skipping patch "{patch}" which is outside manifest dir.'
                 )
                 continue
 
-            if not os.path.exists(patch):
+            if not patch_path.exists():
                 self._log_project(f"Skipping non-existent patch {patch}")
                 continue
 
-            apply_patch(patch, root=self.local_path)
-            self._log_project(f'Applied patch "{patch}"')
-            applied_patches.append(patch)
+            normalized_patch_path = str(patch_path.relative_to(manifest_dir).as_posix())
+
+            apply_patch(normalized_patch_path, root=self.local_path)
+            self._log_project(f'Applied patch "{normalized_patch_path}"')
+            applied_patches.append(normalized_patch_path)
         return applied_patches
 
     def check_for_update(