Module records and aliases

Installation records what a module reports about itself. dpm_install_module
opens a module once, writes its version and description to a .meta file in
/var/lib/dpm/metadata/, and records the alternate names it declared in
modules.aliases beside it. dpm_uninstall_module removes both, leaving the
module file in place.

dpm_list_modules reads those records and opens no module. A module with no
record lists with a version of <uninstalled> and still loads when a caller
names it. An unreadable or absent metadata directory costs the listing its
detail and costs nothing else.

Aliases give a module alternate names, declared through the new
dpm_module_aliases contract symbol or added with dpm_add_module_alias. A
name is recorded once: one already serving as an alias, or belonging to an
installed module, is refused rather than repointed. dpm_require matches a
name against the installed modules, then the alias table, then the module
path.

The metadata directory is a fifth override field and the -M flag, and
[modules] metadata in core.conf.

The test suite is four binaries covering context, modules, records, and
aliases, each a ctest case of its own, alongside the CLI cases.

include/internal/aliases.hpp

@@ -0,0 +1,85 @@
+/**
+ * @file aliases.hpp
+ * @brief The alias table: alternate names a module answers to
+ *
+ * @copyright Copyright (c) 2026 SILO GROUP LLC
+ * @author Chris Punches <chris.punches@silogroup.org>
+ *
+ * Part of the Dark Horse Linux Package Manager (DPM)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+#pragma once
+
+#include <dpm/core.h>
+
+#include <string>
+#include <vector>
+
+struct dpm_ctx;
+
+/** @brief Enumeration cursor over alias table entries */
+struct dpm_alias_cursor {
+    /** One entry per alias the cursor reports. */
+    std::vector<dpm_alias_info> infos;
+
+    /** Backing strings, so the reported pointers stay valid. */
+    std::vector<std::pair<std::string, std::string>> storage;
+
+    /** Position of the next entry. */
+    size_t idx = 0;
+};
+
+namespace dpm_core {
+    /**
+     * @brief Reads the alias table out of a context's metadata directory
+     *
+     * The table is modules.aliases, one `alias = module` per line. A
+     * missing or unreadable file leaves the context holding no aliases,
+     * which costs those alternate names and costs nothing else.
+     *
+     * @param ctx The libdpm-core.so context
+     */
+    void alias_load_table(dpm_ctx* ctx);
+
+    /**
+     * @brief Writes the context's alias table back to disk
+     *
+     * @param ctx The libdpm-core.so context
+     * @param reason Receives the failure reason when the write fails
+     * @return true on success
+     */
+    bool alias_write_table(dpm_ctx* ctx, std::string& reason);
+
+    /**
+     * @brief Resolves an alias to the module it names
+     *
+     * @param ctx The libdpm-core.so context
+     * @param alias The alias to resolve
+     * @return The module name, or an empty string when the alias is unknown
+     */
+    std::string alias_resolve(dpm_ctx* ctx, const std::string& alias);
+
+    /**
+     * @brief Splits a module's comma-separated alias list
+     *
+     * The form dpm_module_aliases() returns. Empty entries are dropped
+     * and each surviving name is trimmed, so trailing separators and
+     * spacing cost nothing.
+     *
+     * @param declared The value the module reported; NULL declares none
+     * @return One entry per name the module answers to
+     */
+    std::vector<std::string> alias_split_declared(const char* declared);
+} // namespace dpm_core