fs_path: mock ownership checks

Provide a mock for file ownership for testability.

src/path.c

@@ -2024,6 +2024,13 @@ done:
 	return supported;
 }
 
+static git_path__mock_owner_t mock_owner = GIT_PATH_MOCK_OWNER_NONE;
+
+void git_path__set_owner(git_path__mock_owner_t owner)
+{
+	mock_owner = owner;
+}
+
 #ifdef GIT_WIN32
 static PSID *sid_dup(PSID sid)
 {
@@ -2116,6 +2123,11 @@ int git_path_owner_is_current_user(bool *out, const char *path)
 	PSID owner_sid = NULL, user_sid = NULL;
 	int error = -1;
 
+	if (mock_owner) {
+		*out = (mock_owner == GIT_PATH_MOCK_OWNER_CURRENT_USER);
+		return 0;
+	}
+
 	if ((error = file_owner_sid(&owner_sid, path)) < 0 ||
 	    (error = current_user_sid(&user_sid)) < 0)
 		goto done;
@@ -2133,6 +2145,11 @@ int git_path_owner_is_system(bool *out, const char *path)
 {
 	PSID owner_sid;
 
+	if (mock_owner) {
+		*out = (mock_owner == GIT_PATH_MOCK_OWNER_SYSTEM);
+		return 0;
+	}
+
 	if (file_owner_sid(&owner_sid, path) < 0)
 		return -1;
 
@@ -2148,6 +2165,12 @@ int git_path_owner_is_system_or_current_user(bool *out, const char *path)
 	PSID owner_sid = NULL, user_sid = NULL;
 	int error = -1;
 
+	if (mock_owner) {
+		*out = (mock_owner == GIT_PATH_MOCK_OWNER_SYSTEM ||
+		        mock_owner == GIT_PATH_MOCK_OWNER_CURRENT_USER);
+		return 0;
+	}
+
 	if (file_owner_sid(&owner_sid, path) < 0)
 		goto done;
 
@@ -2200,18 +2223,37 @@ static int path_owner_is(bool *out, const char *path, uid_t *uids, size_t uids_l
 int git_path_owner_is_current_user(bool *out, const char *path)
 {
 	uid_t userid = geteuid();
+
+	if (mock_owner) {
+		*out = (mock_owner == GIT_PATH_MOCK_OWNER_CURRENT_USER);
+		return 0;
+	}
+
 	return path_owner_is(out, path, &userid, 1);
 }
 
 int git_path_owner_is_system(bool *out, const char *path)
 {
 	uid_t userid = 0;
+
+	if (mock_owner) {
+		*out = (mock_owner == GIT_PATH_MOCK_OWNER_SYSTEM);
+		return 0;
+	}
+
 	return path_owner_is(out, path, &userid, 1);
 }
 
 int git_path_owner_is_system_or_current_user(bool *out, const char *path)
 {
 	uid_t userids[2] = { geteuid(), 0 };
+
+	if (mock_owner) {
+		*out = (mock_owner == GIT_PATH_MOCK_OWNER_SYSTEM ||
+		        mock_owner == GIT_PATH_MOCK_OWNER_CURRENT_USER);
+		return 0;
+	}
+
 	return path_owner_is(out, path, userids, 2);
 }
 

src/path.h

@@ -722,6 +722,20 @@ int git_path_normalize_slashes(git_buf *out, const char *path);
 
 bool git_path_supports_symlinks(const char *dir);
 
+typedef enum {
+	GIT_PATH_MOCK_OWNER_NONE = 0, /* do filesystem lookups as normal */
+	GIT_PATH_MOCK_OWNER_SYSTEM = 1,
+	GIT_PATH_MOCK_OWNER_CURRENT_USER = 2,
+	GIT_PATH_MOCK_OWNER_OTHER = 3
+} git_path__mock_owner_t;
+
+/**
+ * Sets the mock ownership for files; subsequent calls to
+ * `git_path_owner_is_*` functions will return this data until cleared
+ * with `GIT_PATH_MOCK_OWNER_NONE`.
+ */
+void git_path__set_owner(git_path__mock_owner_t owner);
+
 /**
  * Verify that the file in question is owned by an administrator or system
  * account.